When multiple programs are attached, each program receives the return
value from the previous program on the stack and the last program
provides the return value to the attached function.
The fmod_ret bpf programs are run after the fentry programs and before
the fexit programs. The original function is only called if all the
fmod_ret programs return 0 to avoid any unintended side-effects. The
success value, i.e. 0 is not currently configurable but can be made so
where user-space can specify it at load time.
For example:
int func_to_be_attached(int a, int b)
{ <--- do_fentry
do_fmod_ret:
<update ret by calling fmod_ret>
if (ret != 0)
goto do_fexit;
original_function:
<side_effects_happen_here>
} <--- do_fexit
The fmod_ret program attached to this function can be defined as:
SEC("fmod_ret/func_to_be_attached")
int BPF_PROG(func_name, int a, int b, int ret)
{
// This will skip the original function logic.
return 1;
}
The first fmod_ret program is passed 0 in its return argument.
Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200304191853.1529-4-kpsingh@chromium.org
Aside of the general unsafety of run-time map allocation for
instrumentation type programs RT enabled kernels have another constraint:
The instrumentation programs are invoked with preemption disabled, but the
memory allocator spinlocks cannot be acquired in atomic context because
they are converted to 'sleeping' spinlocks on RT.
Therefore enforce map preallocation for these programs types when RT is
enabled.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200224145642.648784007@linutronix.de
The assumption that only programs attached to perf NMI events can deadlock
on memory allocators is wrong. Assume the following simplified callchain:
kmalloc() from regular non BPF context
cache empty
freelist empty
lock(zone->lock);
tracepoint or kprobe
BPF()
update_elem()
lock(bucket)
kmalloc()
cache empty
freelist empty
lock(zone->lock); <- DEADLOCK
There are other ways which do not involve locking to create wreckage:
kmalloc() from regular non BPF context
local_irq_save();
...
obj = slab_first();
kprobe()
BPF()
update_elem()
lock(bucket)
kmalloc()
local_irq_save();
...
obj = slab_first(); <- Same object as above ...
So preallocation _must_ be enforced for all variants of intrusive
instrumentation.
Unfortunately immediate enforcement would break backwards compatibility, so
for now such programs still are allowed to run, but a one time warning is
emitted in dmesg and the verifier emits a warning in the verifier log as
well so developers are made aware about this and can fix their programs
before the enforcement becomes mandatory.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200224145642.540542802@linutronix.de
SOCKMAP & SOCKHASH now support storing references to listening
sockets. Nothing keeps us from using these map types a collection of
sockets to select from in BPF reuseport programs. Whitelist the map types
with the bpf_sk_select_reuseport helper.
The restriction that the socket has to be a member of a reuseport group
still applies. Sockets in SOCKMAP/SOCKHASH that don't have sk_reuseport_cb
set are not a valid target and we signal it with -EINVAL.
The main benefit from this change is that, in contrast to
REUSEPORT_SOCKARRAY, SOCK{MAP,HASH} don't impose a restriction that a
listening socket can be just one BPF map at the same time.
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200218171023.844439-9-jakub@cloudflare.com
Alexei Starovoitov says:
====================
pull-request: bpf-next 2020-01-22
The following pull-request contains BPF updates for your *net-next* tree.
We've added 92 non-merge commits during the last 16 day(s) which contain
a total of 320 files changed, 7532 insertions(+), 1448 deletions(-).
The main changes are:
1) function by function verification and program extensions from Alexei.
2) massive cleanup of selftests/bpf from Toke and Andrii.
3) batched bpf map operations from Brian and Yonghong.
4) tcp congestion control in bpf from Martin.
5) bulking for non-map xdp_redirect form Toke.
6) bpf_send_signal_thread helper from Yonghong.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch adds a helper to read the 64bit jiffies. It will be used
in a later patch to implement the bpf_cubic.c.
The helper is inlined for jit_requested and 64 BITS_PER_LONG
as the map_gen_lookup(). Other cases could be considered together
with map_gen_lookup() if needed.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200122233646.903260-1-kafai@fb.com
Introduce dynamic program extensions. The users can load additional BPF
functions and replace global functions in previously loaded BPF programs while
these programs are executing.
Global functions are verified individually by the verifier based on their types only.
Hence the global function in the new program which types match older function can
safely replace that corresponding function.
This new function/program is called 'an extension' of old program. At load time
the verifier uses (attach_prog_fd, attach_btf_id) pair to identify the function
to be replaced. The BPF program type is derived from the target program into
extension program. Technically bpf_verifier_ops is copied from target program.
The BPF_PROG_TYPE_EXT program type is a placeholder. It has empty verifier_ops.
The extension program can call the same bpf helper functions as target program.
Single BPF_PROG_TYPE_EXT type is used to extend XDP, SKB and all other program
types. The verifier allows only one level of replacement. Meaning that the
extension program cannot recursively extend an extension. That also means that
the maximum stack size is increasing from 512 to 1024 bytes and maximum
function nesting level from 8 to 16. The programs don't always consume that
much. The stack usage is determined by the number of on-stack variables used by
the program. The verifier could have enforced 512 limit for combined original
plus extension program, but it makes for difficult user experience. The main
use case for extensions is to provide generic mechanism to plug external
programs into policy program or function call chaining.
BPF trampoline is used to track both fentry/fexit and program extensions
because both are using the same nop slot at the beginning of every BPF
function. Attaching fentry/fexit to a function that was replaced is not
allowed. The opposite is true as well. Replacing a function that currently
being analyzed with fentry/fexit is not allowed. The executable page allocated
by BPF trampoline is not used by program extensions. This inefficiency will be
optimized in future patches.
Function by function verification of global function supports scalars and
pointer to context only. Hence program extensions are supported for such class
of global functions only. In the future the verifier will be extended with
support to pointers to structures, arrays with sizes, etc.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20200121005348.2769920-2-ast@kernel.org
Restore the 'if (env->cur_state)' check that was incorrectly removed during
code move. Under memory pressure env->cur_state can be freed and zeroed inside
do_check(). Hence the check is necessary.
Fixes: 51c39bb1d5 ("bpf: Introduce function-by-function verification")
Reported-by: syzbot+b296579ba5015704d9fa@syzkaller.appspotmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200122024138.3385590-1-ast@kernel.org
Anatoly has been fuzzing with kBdysch harness and reported a hang in one
of the outcomes:
0: R1=ctx(id=0,off=0,imm=0) R10=fp0
0: (85) call bpf_get_socket_cookie#46
1: R0_w=invP(id=0) R10=fp0
1: (57) r0 &= 808464432
2: R0_w=invP(id=0,umax_value=808464432,var_off=(0x0; 0x30303030)) R10=fp0
2: (14) w0 -= 810299440
3: R0_w=invP(id=0,umax_value=4294967295,var_off=(0xcf800000; 0x3077fff0)) R10=fp0
3: (c4) w0 s>>= 1
4: R0_w=invP(id=0,umin_value=1740636160,umax_value=2147221496,var_off=(0x67c00000; 0x183bfff8)) R10=fp0
4: (76) if w0 s>= 0x30303030 goto pc+216
221: R0_w=invP(id=0,umin_value=1740636160,umax_value=2147221496,var_off=(0x67c00000; 0x183bfff8)) R10=fp0
221: (95) exit
processed 6 insns (limit 1000000) [...]
Taking a closer look, the program was xlated as follows:
# ./bpftool p d x i 12
0: (85) call bpf_get_socket_cookie#7800896
1: (bf) r6 = r0
2: (57) r6 &= 808464432
3: (14) w6 -= 810299440
4: (c4) w6 s>>= 1
5: (76) if w6 s>= 0x30303030 goto pc+216
6: (05) goto pc-1
7: (05) goto pc-1
8: (05) goto pc-1
[...]
220: (05) goto pc-1
221: (05) goto pc-1
222: (95) exit
Meaning, the visible effect is very similar to f54c7898ed ("bpf: Fix
precision tracking for unbounded scalars"), that is, the fall-through
branch in the instruction 5 is considered to be never taken given the
conclusion from the min/max bounds tracking in w6, and therefore the
dead-code sanitation rewrites it as goto pc-1. However, real-life input
disagrees with verification analysis since a soft-lockup was observed.
The bug sits in the analysis of the ARSH. The definition is that we shift
the target register value right by K bits through shifting in copies of
its sign bit. In adjust_scalar_min_max_vals(), we do first coerce the
register into 32 bit mode, same happens after simulating the operation.
However, for the case of simulating the actual ARSH, we don't take the
mode into account and act as if it's always 64 bit, but location of sign
bit is different:
dst_reg->smin_value >>= umin_val;
dst_reg->smax_value >>= umin_val;
dst_reg->var_off = tnum_arshift(dst_reg->var_off, umin_val);
Consider an unknown R0 where bpf_get_socket_cookie() (or others) would
for example return 0xffff. With the above ARSH simulation, we'd see the
following results:
[...]
1: R1=ctx(id=0,off=0,imm=0) R2_w=invP65535 R10=fp0
1: (85) call bpf_get_socket_cookie#46
2: R0_w=invP(id=0) R10=fp0
2: (57) r0 &= 808464432
-> R0_runtime = 0x3030
3: R0_w=invP(id=0,umax_value=808464432,var_off=(0x0; 0x30303030)) R10=fp0
3: (14) w0 -= 810299440
-> R0_runtime = 0xcfb40000
4: R0_w=invP(id=0,umax_value=4294967295,var_off=(0xcf800000; 0x3077fff0)) R10=fp0
(0xffffffff)
4: (c4) w0 s>>= 1
-> R0_runtime = 0xe7da0000
5: R0_w=invP(id=0,umin_value=1740636160,umax_value=2147221496,var_off=(0x67c00000; 0x183bfff8)) R10=fp0
(0x67c00000) (0x7ffbfff8)
[...]
In insn 3, we have a runtime value of 0xcfb40000, which is '1100 1111 1011
0100 0000 0000 0000 0000', the result after the shift has 0xe7da0000 that
is '1110 0111 1101 1010 0000 0000 0000 0000', where the sign bit is correctly
retained in 32 bit mode. In insn4, the umax was 0xffffffff, and changed into
0x7ffbfff8 after the shift, that is, '0111 1111 1111 1011 1111 1111 1111 1000'
and means here that the simulation didn't retain the sign bit. With above
logic, the updates happen on the 64 bit min/max bounds and given we coerced
the register, the sign bits of the bounds are cleared as well, meaning, we
need to force the simulation into s32 space for 32 bit alu mode.
Verification after the fix below. We're first analyzing the fall-through branch
on 32 bit signed >= test eventually leading to rejection of the program in this
specific case:
0: R1=ctx(id=0,off=0,imm=0) R10=fp0
0: (b7) r2 = 808464432
1: R1=ctx(id=0,off=0,imm=0) R2_w=invP808464432 R10=fp0
1: (85) call bpf_get_socket_cookie#46
2: R0_w=invP(id=0) R10=fp0
2: (bf) r6 = r0
3: R0_w=invP(id=0) R6_w=invP(id=0) R10=fp0
3: (57) r6 &= 808464432
4: R0_w=invP(id=0) R6_w=invP(id=0,umax_value=808464432,var_off=(0x0; 0x30303030)) R10=fp0
4: (14) w6 -= 810299440
5: R0_w=invP(id=0) R6_w=invP(id=0,umax_value=4294967295,var_off=(0xcf800000; 0x3077fff0)) R10=fp0
5: (c4) w6 s>>= 1
6: R0_w=invP(id=0) R6_w=invP(id=0,umin_value=3888119808,umax_value=4294705144,var_off=(0xe7c00000; 0x183bfff8)) R10=fp0
(0x67c00000) (0xfffbfff8)
6: (76) if w6 s>= 0x30303030 goto pc+216
7: R0_w=invP(id=0) R6_w=invP(id=0,umin_value=3888119808,umax_value=4294705144,var_off=(0xe7c00000; 0x183bfff8)) R10=fp0
7: (30) r0 = *(u8 *)skb[808464432]
BPF_LD_[ABS|IND] uses reserved fields
processed 8 insns (limit 1000000) [...]
Fixes: 9cbe1f5a32 ("bpf/verifier: improve register value range tracking with ARSH")
Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200115204733.16648-1-daniel@iogearbox.net
New llvm and old llvm with libbpf help produce BTF that distinguish global and
static functions. Unlike arguments of static function the arguments of global
functions cannot be removed or optimized away by llvm. The compiler has to use
exactly the arguments specified in a function prototype. The argument type
information allows the verifier validate each global function independently.
For now only supported argument types are pointer to context and scalars. In
the future pointers to structures, sizes, pointer to packet data can be
supported as well. Consider the following example:
static int f1(int ...)
{
...
}
int f3(int b);
int f2(int a)
{
f1(a) + f3(a);
}
int f3(int b)
{
...
}
int main(...)
{
f1(...) + f2(...) + f3(...);
}
The verifier will start its safety checks from the first global function f2().
It will recursively descend into f1() because it's static. Then it will check
that arguments match for the f3() invocation inside f2(). It will not descend
into f3(). It will finish f2() that has to be successfully verified for all
possible values of 'a'. Then it will proceed with f3(). That function also has
to be safe for all possible values of 'b'. Then it will start subprog 0 (which
is main() function). It will recursively descend into f1() and will skip full
check of f2() and f3(), since they are global. The order of processing global
functions doesn't affect safety, since all global functions must be proven safe
based on their arguments only.
Such function by function verification can drastically improve speed of the
verification and reduce complexity.
Note that the stack limit of 512 still applies to the call chain regardless whether
functions were static or global. The nested level of 8 also still applies. The
same recursion prevention checks are in place as well.
The type information and static/global kind is preserved after the verification
hence in the above example global function f2() and f3() can be replaced later
by equivalent functions with the same types that are loaded and verified later
without affecting safety of this main() program. Such replacement (re-linking)
of global functions is a subject of future patches.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200110064124.1760511-3-ast@kernel.org
The patch introduces BPF_MAP_TYPE_STRUCT_OPS. The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.
The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code). For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
refcount_t refcnt;
enum bpf_struct_ops_state state;
struct tcp_congestion_ops data; /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case). This "value" struct
is created automatically by a macro. Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem). The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".
Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
running kernel.
Instead of reusing the attr->btf_value_type_id,
btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
used as the "user" btf which could store other useful sysadmin/debug
info that may be introduced in the furture,
e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
in the running kernel btf. Populate the value of this object.
The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
the map value. The key is always "0".
During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated. BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem. The map will not allow further update
from this point.
Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".
Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0". The map value returned will
have the prog _id_ populated as the func ptr.
The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)
The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ". This patch uses a separate refcnt
for the purose of tracking the subsystem usage. Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage. However, that will also tie down the
future semantics of map->refcnt and map->usercnt.
The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt. When the very last subsystem's refcnt
is gone, it will also release the map->refcnt. All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).
Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops name dctcp flags 0x0
key 4B value 256B max_entries 1 memlock 4096B
btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
"value": {
"refcnt": {
"refs": {
"counter": 1
}
},
"state": 1,
"data": {
"list": {
"next": 0,
"prev": 0
},
"key": 0,
"flags": 2,
"init": 24,
"release": 0,
"ssthresh": 25,
"cong_avoid": 30,
"set_state": 27,
"cwnd_event": 28,
"in_ack_event": 26,
"undo_cwnd": 29,
"pkts_acked": 0,
"min_tso_segs": 0,
"sndbuf_expand": 0,
"cong_control": 0,
"get_info": 0,
"name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
],
"owner": 0
}
}
}
]
Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
It does an inplace update on "*value" instead returning a pointer
to syscall.c. Otherwise, it needs a separate copy of "zero" value
for the BPF_STRUCT_OPS_STATE_INIT to avoid races.
* The bpf_struct_ops_map_delete_elem() is also called without
preempt_disable() from map_delete_elem(). It is because
the "->unreg()" may requires sleepable context, e.g.
the "tcp_unregister_congestion_control()".
* "const" is added to some of the existing "struct btf_func_model *"
function arg to avoid a compiler warning caused by this patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
This patch allows the kernel's struct ops (i.e. func ptr) to be
implemented in BPF. The first use case in this series is the
"struct tcp_congestion_ops" which will be introduced in a
latter patch.
This patch introduces a new prog type BPF_PROG_TYPE_STRUCT_OPS.
The BPF_PROG_TYPE_STRUCT_OPS prog is verified against a particular
func ptr of a kernel struct. The attr->attach_btf_id is the btf id
of a kernel struct. The attr->expected_attach_type is the member
"index" of that kernel struct. The first member of a struct starts
with member index 0. That will avoid ambiguity when a kernel struct
has multiple func ptrs with the same func signature.
For example, a BPF_PROG_TYPE_STRUCT_OPS prog is written
to implement the "init" func ptr of the "struct tcp_congestion_ops".
The attr->attach_btf_id is the btf id of the "struct tcp_congestion_ops"
of the _running_ kernel. The attr->expected_attach_type is 3.
The ctx of BPF_PROG_TYPE_STRUCT_OPS is an array of u64 args saved
by arch_prepare_bpf_trampoline that will be done in the next
patch when introducing BPF_MAP_TYPE_STRUCT_OPS.
"struct bpf_struct_ops" is introduced as a common interface for the kernel
struct that supports BPF_PROG_TYPE_STRUCT_OPS prog. The supporting kernel
struct will need to implement an instance of the "struct bpf_struct_ops".
The supporting kernel struct also needs to implement a bpf_verifier_ops.
During BPF_PROG_LOAD, bpf_struct_ops_find() will find the right
bpf_verifier_ops by searching the attr->attach_btf_id.
A new "btf_struct_access" is also added to the bpf_verifier_ops such
that the supporting kernel struct can optionally provide its own specific
check on accessing the func arg (e.g. provide limited write access).
After btf_vmlinux is parsed, the new bpf_struct_ops_init() is called
to initialize some values (e.g. the btf id of the supporting kernel
struct) and it can only be done once the btf_vmlinux is available.
The R0 checks at BPF_EXIT is excluded for the BPF_PROG_TYPE_STRUCT_OPS prog
if the return type of the prog->aux->attach_func_proto is "void".
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003503.3855825-1-kafai@fb.com
This patch makes the verifier save the PTR_TO_BTF_ID register state when
spilling to the stack.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003454.3854870-1-kafai@fb.com
Anatoly has been fuzzing with kBdysch harness and reported a hang in one
of the outcomes. Upon closer analysis, it turns out that precise scalar
value tracking is missing a few precision markings for unknown scalars:
0: R1=ctx(id=0,off=0,imm=0) R10=fp0
0: (b7) r0 = 0
1: R0_w=invP0 R1=ctx(id=0,off=0,imm=0) R10=fp0
1: (35) if r0 >= 0xf72e goto pc+0
--> only follow fallthrough
2: R0_w=invP0 R1=ctx(id=0,off=0,imm=0) R10=fp0
2: (35) if r0 >= 0x80fe0000 goto pc+0
--> only follow fallthrough
3: R0_w=invP0 R1=ctx(id=0,off=0,imm=0) R10=fp0
3: (14) w0 -= -536870912
4: R0_w=invP536870912 R1=ctx(id=0,off=0,imm=0) R10=fp0
4: (0f) r1 += r0
5: R0_w=invP536870912 R1_w=inv(id=0) R10=fp0
5: (55) if r1 != 0x104c1500 goto pc+0
--> push other branch for later analysis
R0_w=invP536870912 R1_w=inv273421568 R10=fp0
6: R0_w=invP536870912 R1_w=inv273421568 R10=fp0
6: (b7) r0 = 0
7: R0=invP0 R1=inv273421568 R10=fp0
7: (76) if w1 s>= 0xffffff00 goto pc+3
--> only follow goto
11: R0=invP0 R1=inv273421568 R10=fp0
11: (95) exit
6: R0_w=invP536870912 R1_w=inv(id=0) R10=fp0
6: (b7) r0 = 0
propagating r0
7: safe
processed 11 insns [...]
In the analysis of the second path coming after the successful exit above,
the path is being pruned at line 7. Pruning analysis found that both r0 are
precise P0 and both R1 are non-precise scalars and given prior path with
R1 as non-precise scalar succeeded, this one is therefore safe as well.
However, problem is that given condition at insn 7 in the first run, we only
followed goto and didn't push the other branch for later analysis, we've
never walked the few insns in there and therefore dead-code sanitation
rewrites it as goto pc-1, causing the hang depending on the skb address
hitting these conditions. The issue is that R1 should have been marked as
precise as well such that pruning enforces range check and conluded that new
R1 is not in range of old R1. In insn 4, we mark R1 (skb) as unknown scalar
via __mark_reg_unbounded() but not mark_reg_unbounded() and therefore
regs->precise remains as false.
Back in b5dc0163d8 ("bpf: precise scalar_value tracking"), this was not
the case since marking out of __mark_reg_unbounded() had this covered as well.
Once in both are set as precise in 4 as they should have been, we conclude
that given R1 was in prior fall-through path 0x104c1500 and now is completely
unknown, the check at insn 7 concludes that we need to continue walking.
Analysis after the fix:
0: R1=ctx(id=0,off=0,imm=0) R10=fp0
0: (b7) r0 = 0
1: R0_w=invP0 R1=ctx(id=0,off=0,imm=0) R10=fp0
1: (35) if r0 >= 0xf72e goto pc+0
2: R0_w=invP0 R1=ctx(id=0,off=0,imm=0) R10=fp0
2: (35) if r0 >= 0x80fe0000 goto pc+0
3: R0_w=invP0 R1=ctx(id=0,off=0,imm=0) R10=fp0
3: (14) w0 -= -536870912
4: R0_w=invP536870912 R1=ctx(id=0,off=0,imm=0) R10=fp0
4: (0f) r1 += r0
5: R0_w=invP536870912 R1_w=invP(id=0) R10=fp0
5: (55) if r1 != 0x104c1500 goto pc+0
R0_w=invP536870912 R1_w=invP273421568 R10=fp0
6: R0_w=invP536870912 R1_w=invP273421568 R10=fp0
6: (b7) r0 = 0
7: R0=invP0 R1=invP273421568 R10=fp0
7: (76) if w1 s>= 0xffffff00 goto pc+3
11: R0=invP0 R1=invP273421568 R10=fp0
11: (95) exit
6: R0_w=invP536870912 R1_w=invP(id=0) R10=fp0
6: (b7) r0 = 0
7: R0_w=invP0 R1_w=invP(id=0) R10=fp0
7: (76) if w1 s>= 0xffffff00 goto pc+3
R0_w=invP0 R1_w=invP(id=0) R10=fp0
8: R0_w=invP0 R1_w=invP(id=0) R10=fp0
8: (a5) if r0 < 0x2007002a goto pc+0
9: R0_w=invP0 R1_w=invP(id=0) R10=fp0
9: (57) r0 &= -16316416
10: R0_w=invP0 R1_w=invP(id=0) R10=fp0
10: (a6) if w0 < 0x1201 goto pc+0
11: R0_w=invP0 R1_w=invP(id=0) R10=fp0
11: (95) exit
11: R0=invP0 R1=invP(id=0) R10=fp0
11: (95) exit
processed 16 insns [...]
Fixes: 6754172c20 ("bpf: fix precision tracking in presence of bpf2bpf calls")
Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191222223740.25297-1-daniel@iogearbox.net
While testing Cilium with /unreleased/ Linus' tree under BPF-based NodePort
implementation, I noticed a strange BPF SNAT engine behavior from time to
time. In some cases it would do the correct SNAT/DNAT service translation,
but at a random point in time it would just stop and perform an unexpected
translation after SYN, SYN/ACK and stack would send a RST back. While initially
assuming that there is some sort of a race condition in BPF code, adding
trace_printk()s for debugging purposes at some point seemed to have resolved
the issue auto-magically.
Digging deeper on this Heisenbug and reducing the trace_printk() calls to
an absolute minimum, it turns out that a single call would suffice to
trigger / not trigger the seen RST issue, even though the logic of the
program itself remains unchanged. Turns out the single call changed verifier
pruning behavior to get everything to work. Reconstructing a minimal test
case, the incorrect JIT dump looked as follows:
# bpftool p d j i 11346
0xffffffffc0cba96c:
[...]
21: movzbq 0x30(%rdi),%rax
26: cmp $0xd,%rax
2a: je 0x000000000000003a
2c: xor %edx,%edx
2e: movabs $0xffff89cc74e85800,%rsi
38: jmp 0x0000000000000049
3a: mov $0x2,%edx
3f: movabs $0xffff89cc74e85800,%rsi
49: mov -0x224(%rbp),%eax
4f: cmp $0x20,%eax
52: ja 0x0000000000000062
54: add $0x1,%eax
57: mov %eax,-0x224(%rbp)
5d: jmpq 0xffffffffffff6911
62: mov $0x1,%eax
[...]
Hence, unexpectedly, JIT emitted a direct jump even though retpoline based
one would have been needed since in line 2c and 3a we have different slot
keys in BPF reg r3. Verifier log of the test case reveals what happened:
0: (b7) r0 = 14
1: (73) *(u8 *)(r1 +48) = r0
2: (71) r0 = *(u8 *)(r1 +48)
3: (15) if r0 == 0xd goto pc+4
R0_w=inv(id=0,umax_value=255,var_off=(0x0; 0xff)) R1=ctx(id=0,off=0,imm=0) R10=fp0
4: (b7) r3 = 0
5: (18) r2 = 0xffff89cc74d54a00
7: (05) goto pc+3
11: (85) call bpf_tail_call#12
12: (b7) r0 = 1
13: (95) exit
from 3 to 8: R0_w=inv13 R1=ctx(id=0,off=0,imm=0) R10=fp0
8: (b7) r3 = 2
9: (18) r2 = 0xffff89cc74d54a00
11: safe
processed 13 insns (limit 1000000) [...]
Second branch is pruned by verifier since considered safe, but issue is that
record_func_key() couldn't have seen the index in line 3a and therefore
decided that emitting a direct jump at this location was okay.
Fix this by reusing our backtracking logic for precise scalar verification
in order to prevent pruning on the slot key. This means verifier will track
content of r3 all the way backwards and only prune if both scalars were
unknown in state equivalence check and therefore poisoned in the first place
in record_func_key(). The range is [x,x] in record_func_key() case since
the slot always would have to be constant immediate. Correct verification
after fix:
0: (b7) r0 = 14
1: (73) *(u8 *)(r1 +48) = r0
2: (71) r0 = *(u8 *)(r1 +48)
3: (15) if r0 == 0xd goto pc+4
R0_w=invP(id=0,umax_value=255,var_off=(0x0; 0xff)) R1=ctx(id=0,off=0,imm=0) R10=fp0
4: (b7) r3 = 0
5: (18) r2 = 0x0
7: (05) goto pc+3
11: (85) call bpf_tail_call#12
12: (b7) r0 = 1
13: (95) exit
from 3 to 8: R0_w=invP13 R1=ctx(id=0,off=0,imm=0) R10=fp0
8: (b7) r3 = 2
9: (18) r2 = 0x0
11: (85) call bpf_tail_call#12
12: (b7) r0 = 1
13: (95) exit
processed 15 insns (limit 1000000) [...]
And correct corresponding JIT dump:
# bpftool p d j i 11
0xffffffffc0dc34c4:
[...]
21: movzbq 0x30(%rdi),%rax
26: cmp $0xd,%rax
2a: je 0x000000000000003a
2c: xor %edx,%edx
2e: movabs $0xffff9928b4c02200,%rsi
38: jmp 0x0000000000000049
3a: mov $0x2,%edx
3f: movabs $0xffff9928b4c02200,%rsi
49: cmp $0x4,%rdx
4d: jae 0x0000000000000093
4f: and $0x3,%edx
52: mov %edx,%edx
54: cmp %edx,0x24(%rsi)
57: jbe 0x0000000000000093
59: mov -0x224(%rbp),%eax
5f: cmp $0x20,%eax
62: ja 0x0000000000000093
64: add $0x1,%eax
67: mov %eax,-0x224(%rbp)
6d: mov 0x110(%rsi,%rdx,8),%rax
75: test %rax,%rax
78: je 0x0000000000000093
7a: mov 0x30(%rax),%rax
7e: add $0x19,%rax
82: callq 0x000000000000008e
87: pause
89: lfence
8c: jmp 0x0000000000000087
8e: mov %rax,(%rsp)
92: retq
93: mov $0x1,%eax
[...]
Also explicitly adding explicit env->allow_ptr_leaks to fixup_bpf_calls() since
backtracking is enabled under former (direct jumps as well, but use different
test). In case of only tracking different map pointers as in c93552c443 ("bpf:
properly enforce index mask to prevent out-of-bounds speculation"), pruning
cannot make such short-cuts, neither if there are paths with scalar and non-scalar
types as r3. mark_chain_precision() is only needed after we know that
register_is_const(). If it was not the case, we already poison the key on first
path and non-const key in later paths are not matching the scalar range in regsafe()
either. Cilium NodePort testing passes fine as well now. Note, released kernels
not affected.
Fixes: d2e4c1e6c2 ("bpf: Constant map key tracking for prog array pokes")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/ac43ffdeb7386c5bd688761ed266f3722bb39823.1576789878.git.daniel@iogearbox.net
Recently noticed that we're tracking programs related to local storage maps
through their prog pointer. This is a wrong assumption since the prog pointer
can still change throughout the verification process, for example, whenever
bpf_patch_insn_single() is called.
Therefore, the prog pointer that was assigned via bpf_cgroup_storage_assign()
is not guaranteed to be the same as we pass in bpf_cgroup_storage_release()
and the map would therefore remain in busy state forever. Fix this by using
the prog's aux pointer which is stable throughout verification and beyond.
Fixes: de9cbbaadb ("bpf: introduce cgroup storage maps")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/1471c69eca3022218666f909bc927a92388fd09e.1576580332.git.daniel@iogearbox.net
Commit da765a2f59 ("bpf: Add poke dependency tracking for prog array
maps") wrongly assumed that in case of prog load errors, we're cleaning
up all program tracking via bpf_free_used_maps().
However, it can happen that we're still at the point where we didn't copy
map pointers into the prog's aux section such that env->prog->aux->used_maps
is still zero, running into a UAF. In such case, the verifier has similar
release_maps() helper that drops references to used maps from its env.
Consolidate the release code into __bpf_free_used_maps() and call it from
all sides to fix it.
Fixes: da765a2f59 ("bpf: Add poke dependency tracking for prog array maps")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/1c2909484ca524ae9f55109b06f22b6213e76376.1576514756.git.daniel@iogearbox.net
For jited bpf program, if the subprogram count is 1, i.e.,
there is no callees in the program, prog->aux->func will be NULL
and prog->bpf_func points to image address of the program.
If there is more than one subprogram, prog->aux->func is populated,
and subprogram 0 can be accessed through either prog->bpf_func or
prog->aux->func[0]. Other subprograms should be accessed through
prog->aux->func[subprog_id].
This patch fixed a bug in check_attach_btf_id(), where
prog->aux->func[subprog_id] is used to access any subprogram which
caused a segfault like below:
[79162.619208] BUG: kernel NULL pointer dereference, address:
0000000000000000
......
[79162.634255] Call Trace:
[79162.634974] ? _cond_resched+0x15/0x30
[79162.635686] ? kmem_cache_alloc_trace+0x162/0x220
[79162.636398] ? selinux_bpf_prog_alloc+0x1f/0x60
[79162.637111] bpf_prog_load+0x3de/0x690
[79162.637809] __do_sys_bpf+0x105/0x1740
[79162.638488] do_syscall_64+0x5b/0x180
[79162.639147] entry_SYSCALL_64_after_hwframe+0x44/0xa9
......
Fixes: 5b92a28aae ("bpf: Support attaching tracing BPF program to other BPF programs")
Reported-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191205010606.177774-1-yhs@fb.com
Add tracking of constant keys into tail call maps. The signature of
bpf_tail_call_proto is that arg1 is ctx, arg2 map pointer and arg3
is a index key. The direct call approach for tail calls can be enabled
if the verifier asserted that for all branches leading to the tail call
helper invocation, the map pointer and index key were both constant
and the same.
Tracking of map pointers we already do from prior work via c93552c443
("bpf: properly enforce index mask to prevent out-of-bounds speculation")
and 09772d92cd ("bpf: avoid retpoline for lookup/update/ delete calls
on maps").
Given the tail call map index key is not on stack but directly in the
register, we can add similar tracking approach and later in fixup_bpf_calls()
add a poke descriptor to the progs poke_tab with the relevant information
for the JITing phase.
We internally reuse insn->imm for the rewritten BPF_JMP | BPF_TAIL_CALL
instruction in order to point into the prog's poke_tab, and keep insn->imm
as 0 as indicator that current indirect tail call emission must be used.
Note that publishing to the tracker must happen at the end of fixup_bpf_calls()
since adding elements to the poke_tab reallocates its memory, so we need
to wait until its in final state.
Future work can generalize and add similar approach to optimize plain
array map lookups. Difference there is that we need to look into the key
value that sits on stack. For clarity in bpf_insn_aux_data, map_state
has been renamed into map_ptr_state, so we get map_{ptr,key}_state as
trackers.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/e8db37f6b2ae60402fa40216c96738ee9b316c32.1574452833.git.daniel@iogearbox.net
With latest llvm (trunk https://github.com/llvm/llvm-project),
test_progs, which has +alu32 enabled, failed for strobemeta.o.
The verifier output looks like below with edit to replace large
decimal numbers with hex ones.
193: (85) call bpf_probe_read_user_str#114
R0=inv(id=0)
194: (26) if w0 > 0x1 goto pc+4
R0_w=inv(id=0,umax_value=0xffffffff00000001)
195: (6b) *(u16 *)(r7 +80) = r0
196: (bc) w6 = w0
R6_w=inv(id=0,umax_value=0xffffffff,var_off=(0x0; 0xffffffff))
197: (67) r6 <<= 32
R6_w=inv(id=0,smax_value=0x7fffffff00000000,umax_value=0xffffffff00000000,
var_off=(0x0; 0xffffffff00000000))
198: (77) r6 >>= 32
R6=inv(id=0,umax_value=0xffffffff,var_off=(0x0; 0xffffffff))
...
201: (79) r8 = *(u64 *)(r10 -416)
R8_w=map_value(id=0,off=40,ks=4,vs=13872,imm=0)
202: (0f) r8 += r6
R8_w=map_value(id=0,off=40,ks=4,vs=13872,umax_value=0xffffffff,var_off=(0x0; 0xffffffff))
203: (07) r8 += 9696
R8_w=map_value(id=0,off=9736,ks=4,vs=13872,umax_value=0xffffffff,var_off=(0x0; 0xffffffff))
...
255: (bf) r1 = r8
R1_w=map_value(id=0,off=9736,ks=4,vs=13872,umax_value=0xffffffff,var_off=(0x0; 0xffffffff))
...
257: (85) call bpf_probe_read_user_str#114
R1 unbounded memory access, make sure to bounds check any array access into a map
The value range for register r6 at insn 198 should be really just 0/1.
The umax_value=0xffffffff caused later verification failure.
After jmp instructions, the current verifier already tried to use just
obtained information to get better register range. The current mechanism is
for 64bit register only. This patch implemented to tighten the range
for 32bit sub-registers after jmp32 instructions.
With the patch, we have the below range ranges for the
above code sequence:
193: (85) call bpf_probe_read_user_str#114
R0=inv(id=0)
194: (26) if w0 > 0x1 goto pc+4
R0_w=inv(id=0,smax_value=0x7fffffff00000001,umax_value=0xffffffff00000001,
var_off=(0x0; 0xffffffff00000001))
195: (6b) *(u16 *)(r7 +80) = r0
196: (bc) w6 = w0
R6_w=inv(id=0,umax_value=0xffffffff,var_off=(0x0; 0x1))
197: (67) r6 <<= 32
R6_w=inv(id=0,umax_value=0x100000000,var_off=(0x0; 0x100000000))
198: (77) r6 >>= 32
R6=inv(id=0,umax_value=1,var_off=(0x0; 0x1))
...
201: (79) r8 = *(u64 *)(r10 -416)
R8_w=map_value(id=0,off=40,ks=4,vs=13872,imm=0)
202: (0f) r8 += r6
R8_w=map_value(id=0,off=40,ks=4,vs=13872,umax_value=1,var_off=(0x0; 0x1))
203: (07) r8 += 9696
R8_w=map_value(id=0,off=9736,ks=4,vs=13872,umax_value=1,var_off=(0x0; 0x1))
...
255: (bf) r1 = r8
R1_w=map_value(id=0,off=9736,ks=4,vs=13872,umax_value=1,var_off=(0x0; 0x1))
...
257: (85) call bpf_probe_read_user_str#114
...
At insn 194, the register R0 has better var_off.mask and smax_value.
Especially, the var_off.mask ensures later lshift and rshift
maintains proper value range.
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191121170650.449030-1-yhs@fb.com
92117d8443 ("bpf: fix refcnt overflow") turned refcounting of bpf_map into
potentially failing operation, when refcount reaches BPF_MAX_REFCNT limit
(32k). Due to using 32-bit counter, it's possible in practice to overflow
refcounter and make it wrap around to 0, causing erroneous map free, while
there are still references to it, causing use-after-free problems.
But having a failing refcounting operations are problematic in some cases. One
example is mmap() interface. After establishing initial memory-mapping, user
is allowed to arbitrarily map/remap/unmap parts of mapped memory, arbitrarily
splitting it into multiple non-contiguous regions. All this happening without
any control from the users of mmap subsystem. Rather mmap subsystem sends
notifications to original creator of memory mapping through open/close
callbacks, which are optionally specified during initial memory mapping
creation. These callbacks are used to maintain accurate refcount for bpf_map
(see next patch in this series). The problem is that open() callback is not
supposed to fail, because memory-mapped resource is set up and properly
referenced. This is posing a problem for using memory-mapping with BPF maps.
One solution to this is to maintain separate refcount for just memory-mappings
and do single bpf_map_inc/bpf_map_put when it goes from/to zero, respectively.
There are similar use cases in current work on tcp-bpf, necessitating extra
counter as well. This seems like a rather unfortunate and ugly solution that
doesn't scale well to various new use cases.
Another approach to solve this is to use non-failing refcount_t type, which
uses 32-bit counter internally, but, once reaching overflow state at UINT_MAX,
stays there. This utlimately causes memory leak, but prevents use after free.
But given refcounting is not the most performance-critical operation with BPF
maps (it's not used from running BPF program code), we can also just switch to
64-bit counter that can't overflow in practice, potentially disadvantaging
32-bit platforms a tiny bit. This simplifies semantics and allows above
described scenarios to not worry about failing refcount increment operation.
In terms of struct bpf_map size, we are still good and use the same amount of
space:
BEFORE (3 cache lines, 8 bytes of padding at the end):
struct bpf_map {
const struct bpf_map_ops * ops __attribute__((__aligned__(64))); /* 0 8 */
struct bpf_map * inner_map_meta; /* 8 8 */
void * security; /* 16 8 */
enum bpf_map_type map_type; /* 24 4 */
u32 key_size; /* 28 4 */
u32 value_size; /* 32 4 */
u32 max_entries; /* 36 4 */
u32 map_flags; /* 40 4 */
int spin_lock_off; /* 44 4 */
u32 id; /* 48 4 */
int numa_node; /* 52 4 */
u32 btf_key_type_id; /* 56 4 */
u32 btf_value_type_id; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
struct btf * btf; /* 64 8 */
struct bpf_map_memory memory; /* 72 16 */
bool unpriv_array; /* 88 1 */
bool frozen; /* 89 1 */
/* XXX 38 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
atomic_t refcnt __attribute__((__aligned__(64))); /* 128 4 */
atomic_t usercnt; /* 132 4 */
struct work_struct work; /* 136 32 */
char name[16]; /* 168 16 */
/* size: 192, cachelines: 3, members: 21 */
/* sum members: 146, holes: 1, sum holes: 38 */
/* padding: 8 */
/* forced alignments: 2, forced holes: 1, sum forced holes: 38 */
} __attribute__((__aligned__(64)));
AFTER (same 3 cache lines, no extra padding now):
struct bpf_map {
const struct bpf_map_ops * ops __attribute__((__aligned__(64))); /* 0 8 */
struct bpf_map * inner_map_meta; /* 8 8 */
void * security; /* 16 8 */
enum bpf_map_type map_type; /* 24 4 */
u32 key_size; /* 28 4 */
u32 value_size; /* 32 4 */
u32 max_entries; /* 36 4 */
u32 map_flags; /* 40 4 */
int spin_lock_off; /* 44 4 */
u32 id; /* 48 4 */
int numa_node; /* 52 4 */
u32 btf_key_type_id; /* 56 4 */
u32 btf_value_type_id; /* 60 4 */
/* --- cacheline 1 boundary (64 bytes) --- */
struct btf * btf; /* 64 8 */
struct bpf_map_memory memory; /* 72 16 */
bool unpriv_array; /* 88 1 */
bool frozen; /* 89 1 */
/* XXX 38 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
atomic64_t refcnt __attribute__((__aligned__(64))); /* 128 8 */
atomic64_t usercnt; /* 136 8 */
struct work_struct work; /* 144 32 */
char name[16]; /* 176 16 */
/* size: 192, cachelines: 3, members: 21 */
/* sum members: 154, holes: 1, sum holes: 38 */
/* forced alignments: 2, forced holes: 1, sum forced holes: 38 */
} __attribute__((__aligned__(64)));
This patch, while modifying all users of bpf_map_inc, also cleans up its
interface to match bpf_map_put with separate operations for bpf_map_inc and
bpf_map_inc_with_uref (to match bpf_map_put and bpf_map_put_with_uref,
respectively). Also, given there are no users of bpf_map_inc_not_zero
specifying uref=true, remove uref flag and default to uref=false internally.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191117172806.2195367-2-andriin@fb.com
Allow FENTRY/FEXIT BPF programs to attach to other BPF programs of any type
including their subprograms. This feature allows snooping on input and output
packets in XDP, TC programs including their return values. In order to do that
the verifier needs to track types not only of vmlinux, but types of other BPF
programs as well. The verifier also needs to translate uapi/linux/bpf.h types
used by networking programs into kernel internal BTF types used by FENTRY/FEXIT
BPF programs. In some cases LLVM optimizations can remove arguments from BPF
subprograms without adjusting BTF info that LLVM backend knows. When BTF info
disagrees with actual types that the verifiers sees the BPF trampoline has to
fallback to conservative and treat all arguments as u64. The FENTRY/FEXIT
program can still attach to such subprograms, but it won't be able to recognize
pointer types like 'struct sk_buff *' and it won't be able to pass them to
bpf_skb_output() for dumping packets to user space. The FENTRY/FEXIT program
would need to use bpf_probe_read_kernel() instead.
The BPF_PROG_LOAD command is extended with attach_prog_fd field. When it's set
to zero the attach_btf_id is one vmlinux BTF type ids. When attach_prog_fd
points to previously loaded BPF program the attach_btf_id is BTF type id of
main function or one of its subprograms.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-18-ast@kernel.org
Make the verifier check that BTF types of function arguments match actual types
passed into top-level BPF program and into BPF-to-BPF calls. If types match
such BPF programs and sub-programs will have full support of BPF trampoline. If
types mismatch the trampoline has to be conservative. It has to save/restore
five program arguments and assume 64-bit scalars.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-17-ast@kernel.org
Annotate BPF program context types with program-side type and kernel-side type.
This type information is used by the verifier. btf_get_prog_ctx_type() is
used in the later patches to verify that BTF type of ctx in BPF program matches to
kernel expected ctx type. For example, the XDP program type is:
BPF_PROG_TYPE(BPF_PROG_TYPE_XDP, xdp, struct xdp_md, struct xdp_buff)
That means that XDP program should be written as:
int xdp_prog(struct xdp_md *ctx) { ... }
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-16-ast@kernel.org
btf_resolve_helper_id() caching logic is a bit racy, since under root the
verifier can verify several programs in parallel. Fix it with READ/WRITE_ONCE.
Fix the type as well, since error is also recorded.
Fixes: a7658e1a41 ("bpf: Check types of arguments passed into helpers")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-15-ast@kernel.org
Introduce BPF trampoline concept to allow kernel code to call into BPF programs
with practically zero overhead. The trampoline generation logic is
architecture dependent. It's converting native calling convention into BPF
calling convention. BPF ISA is 64-bit (even on 32-bit architectures). The
registers R1 to R5 are used to pass arguments into BPF functions. The main BPF
program accepts only single argument "ctx" in R1. Whereas CPU native calling
convention is different. x86-64 is passing first 6 arguments in registers
and the rest on the stack. x86-32 is passing first 3 arguments in registers.
sparc64 is passing first 6 in registers. And so on.
The trampolines between BPF and kernel already exist. BPF_CALL_x macros in
include/linux/filter.h statically compile trampolines from BPF into kernel
helpers. They convert up to five u64 arguments into kernel C pointers and
integers. On 64-bit architectures this BPF_to_kernel trampolines are nops. On
32-bit architecture they're meaningful.
The opposite job kernel_to_BPF trampolines is done by CAST_TO_U64 macros and
__bpf_trace_##call() shim functions in include/trace/bpf_probe.h. They convert
kernel function arguments into array of u64s that BPF program consumes via
R1=ctx pointer.
This patch set is doing the same job as __bpf_trace_##call() static
trampolines, but dynamically for any kernel function. There are ~22k global
kernel functions that are attachable via nop at function entry. The function
arguments and types are described in BTF. The job of btf_distill_func_proto()
function is to extract useful information from BTF into "function model" that
architecture dependent trampoline generators will use to generate assembly code
to cast kernel function arguments into array of u64s. For example the kernel
function eth_type_trans has two pointers. They will be casted to u64 and stored
into stack of generated trampoline. The pointer to that stack space will be
passed into BPF program in R1. On x86-64 such generated trampoline will consume
16 bytes of stack and two stores of %rdi and %rsi into stack. The verifier will
make sure that only two u64 are accessed read-only by BPF program. The verifier
will also recognize the precise type of the pointers being accessed and will
not allow typecasting of the pointer to a different type within BPF program.
The tracing use case in the datacenter demonstrated that certain key kernel
functions have (like tcp_retransmit_skb) have 2 or more kprobes that are always
active. Other functions have both kprobe and kretprobe. So it is essential to
keep both kernel code and BPF programs executing at maximum speed. Hence
generated BPF trampoline is re-generated every time new program is attached or
detached to maintain maximum performance.
To avoid the high cost of retpoline the attached BPF programs are called
directly. __bpf_prog_enter/exit() are used to support per-program execution
stats. In the future this logic will be optimized further by adding support
for bpf_stats_enabled_key inside generated assembly code. Introduction of
preemptible and sleepable BPF programs will completely remove the need to call
to __bpf_prog_enter/exit().
Detach of a BPF program from the trampoline should not fail. To avoid memory
allocation in detach path the half of the page is used as a reserve and flipped
after each attach/detach. 2k bytes is enough to call 40+ BPF programs directly
which is enough for BPF tracing use cases. This limit can be increased in the
future.
BPF_TRACE_FENTRY programs have access to raw kernel function arguments while
BPF_TRACE_FEXIT programs have access to kernel return value as well. Often
kprobe BPF program remembers function arguments in a map while kretprobe
fetches arguments from a map and analyzes them together with return value.
BPF_TRACE_FEXIT accelerates this typical use case.
Recursion prevention for kprobe BPF programs is done via per-cpu
bpf_prog_active counter. In practice that turned out to be a mistake. It
caused programs to randomly skip execution. The tracing tools missed results
they were looking for. Hence BPF trampoline doesn't provide builtin recursion
prevention. It's a job of BPF program itself and will be addressed in the
follow up patches.
BPF trampoline is intended to be used beyond tracing and fentry/fexit use cases
in the future. For example to remove retpoline cost from XDP programs.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-5-ast@kernel.org
The bpf program type raw_tp together with 'expected_attach_type'
was the most appropriate api to indicate BTF-enabled raw_tp programs.
But during development it became apparent that 'expected_attach_type'
cannot be used and new 'attach_btf_id' field had to be introduced.
Which means that the information is duplicated in two fields where
one of them is ignored.
Clean it up by introducing new program type where both
'expected_attach_type' and 'attach_btf_id' fields have
specific meaning.
In the future 'expected_attach_type' will be extended
with other attach points that have similar semantics to raw_tp.
This patch is replacing BTF-enabled BPF_PROG_TYPE_RAW_TRACEPOINT with
prog_type = BPF_RPOG_TYPE_TRACING
expected_attach_type = BPF_TRACE_RAW_TP
attach_btf_id = btf_id of raw tracepoint inside the kernel
Future patches will add
expected_attach_type = BPF_TRACE_FENTRY or BPF_TRACE_FEXIT
where programs have the same input context and the same helpers,
but different attach points.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191030223212.953010-2-ast@kernel.org
The return value of raw_tp programs is ignored by __bpf_trace_run()
that calls them. The verifier also allows any value to be returned.
For BTF-enabled raw_tp lets enforce 'return 0', so that return value
can be used for something in the future.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191029032426.1206762-1-ast@kernel.org
This patch makes a few changes to btf_ctx_access() to prepare
it for non raw_tp use case where the attach_btf_id is not
necessary a BTF_KIND_TYPEDEF.
It moves the "btf_trace_" prefix check and typedef-follow logic to a new
function "check_attach_btf_id()" which is called only once during
bpf_check(). btf_ctx_access() only operates on a BTF_KIND_FUNC_PROTO
type now. That should also be more efficient since it is done only
one instead of every-time check_ctx_access() is called.
"check_attach_btf_id()" needs to find the func_proto type from
the attach_btf_id. It needs to store the result into the
newly added prog->aux->attach_func_proto. func_proto
btf type has no name, so a proper name should be stored into
"attach_func_name" also.
v2:
- Move the "btf_trace_" check to an earlier verifier phase (Alexei)
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191025001811.1718491-1-kafai@fb.com
Introduce new helper that reuses existing skb perf_event output
implementation, but can be called from raw_tracepoint programs
that receive 'struct sk_buff *' as tracepoint argument or
can walk other kernel data structures to skb pointer.
In order to do that teach verifier to resolve true C types
of bpf helpers into in-kernel BTF ids.
The type of kernel pointer passed by raw tracepoint into bpf
program will be tracked by the verifier all the way until
it's passed into helper function.
For example:
kfree_skb() kernel function calls trace_kfree_skb(skb, loc);
bpf programs receives that skb pointer and may eventually
pass it into bpf_skb_output() bpf helper which in-kernel is
implemented via bpf_skb_event_output() kernel function.
Its first argument in the kernel is 'struct sk_buff *'.
The verifier makes sure that types match all the way.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191016032505.2089704-11-ast@kernel.org
Pointer to BTF object is a pointer to kernel object or NULL.
Such pointers can only be used by BPF_LDX instructions.
The verifier changed their opcode from LDX|MEM|size
to LDX|PROBE_MEM|size to make JITing easier.
The number of entries in extable is the number of BPF_LDX insns
that access kernel memory via "pointer to BTF type".
Only these load instructions can fault.
Since x86 extable is relative it has to be allocated in the same
memory region as JITed code.
Allocate it prior to last pass of JITing and let the last pass populate it.
Pointer to extable in bpf_prog_aux is necessary to make page fault
handling fast.
Page fault handling is done in two steps:
1. bpf_prog_kallsyms_find() finds BPF program that page faulted.
It's done by walking rb tree.
2. then extable for given bpf program is binary searched.
This process is similar to how page faulting is done for kernel modules.
The exception handler skips over faulting x86 instruction and
initializes destination register with zero. This mimics exact
behavior of bpf_probe_read (when probe_kernel_read faults dest is zeroed).
JITs for other architectures can add support in similar way.
Until then they will reject unknown opcode and fallback to interpreter.
Since extable should be aligned and placed near JITed code
make bpf_jit_binary_alloc() return 4 byte aligned image offset,
so that extable aligning formula in bpf_int_jit_compile() doesn't need
to rely on internal implementation of bpf_jit_binary_alloc().
On x86 gcc defaults to 16-byte alignment for regular kernel functions
due to better performance. JITed code may be aligned to 16 in the future,
but it will use 4 in the meantime.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191016032505.2089704-10-ast@kernel.org
Pointer to BTF object is a pointer to kernel object or NULL.
The memory access in the interpreter has to be done via probe_kernel_read
to avoid page faults.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191016032505.2089704-9-ast@kernel.org
libbpf analyzes bpf C program, searches in-kernel BTF for given type name
and stores it into expected_attach_type.
The kernel verifier expects this btf_id to point to something like:
typedef void (*btf_trace_kfree_skb)(void *, struct sk_buff *skb, void *loc);
which represents signature of raw_tracepoint "kfree_skb".
Then btf_ctx_access() matches ctx+0 access in bpf program with 'skb'
and 'ctx+8' access with 'loc' arguments of "kfree_skb" tracepoint.
In first case it passes btf_id of 'struct sk_buff *' back to the verifier core
and 'void *' in second case.
Then the verifier tracks PTR_TO_BTF_ID as any other pointer type.
Like PTR_TO_SOCKET points to 'struct bpf_sock',
PTR_TO_TCP_SOCK points to 'struct bpf_tcp_sock', and so on.
PTR_TO_BTF_ID points to in-kernel structs.
If 1234 is btf_id of 'struct sk_buff' in vmlinux's BTF
then PTR_TO_BTF_ID#1234 points to one of in kernel skbs.
When PTR_TO_BTF_ID#1234 is dereferenced (like r2 = *(u64 *)r1 + 32)
the btf_struct_access() checks which field of 'struct sk_buff' is
at offset 32. Checks that size of access matches type definition
of the field and continues to track the dereferenced type.
If that field was a pointer to 'struct net_device' the r2's type
will be PTR_TO_BTF_ID#456. Where 456 is btf_id of 'struct net_device'
in vmlinux's BTF.
Such verifier analysis prevents "cheating" in BPF C program.
The program cannot cast arbitrary pointer to 'struct sk_buff *'
and access it. C compiler would allow type cast, of course,
but the verifier will notice type mismatch based on BPF assembly
and in-kernel BTF.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191016032505.2089704-7-ast@kernel.org
If in-kernel BTF exists parse it and prepare 'struct btf *btf_vmlinux'
for further use by the verifier.
In-kernel BTF is trusted just like kallsyms and other build artifacts
embedded into vmlinux.
Yet run this BTF image through BTF verifier to make sure
that it is valid and it wasn't mangled during the build.
If in-kernel BTF is incorrect it means either gcc or pahole or kernel
are buggy. In such case disallow loading BPF programs.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191016032505.2089704-4-ast@kernel.org
Fix "warning: cast to pointer from integer of different size" when
casting u64 addr to void *.
Fixes: a23740ec43 ("bpf: Track contents of read-only maps as scalars")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191011172053.2980619-1-andriin@fb.com
Maps that are read-only both from BPF program side and user space side
have their contents constant, so verifier can track referenced values
precisely and use that knowledge for dead code elimination, branch
pruning, etc. This patch teaches BPF verifier how to do this.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191009201458.2679171-2-andriin@fb.com
Daniel Borkmann says:
====================
pull-request: bpf-next 2019-09-16
The following pull-request contains BPF updates for your *net-next* tree.
The main changes are:
1) Now that initial BPF backend for gcc has been merged upstream, enable
BPF kselftest suite for bpf-gcc. Also fix a BE issue with access to
bpf_sysctl.file_pos, from Ilya.
2) Follow-up fix for link-vmlinux.sh to remove bash-specific extensions
related to recent work on exposing BTF info through sysfs, from Andrii.
3) AF_XDP zero copy fixes for i40e and ixgbe driver which caused umem
headroom to be added twice, from Ciara.
4) Refactoring work to convert sock opt tests into test_progs framework
in BPF kselftests, from Stanislav.
5) Fix a general protection fault in dev_map_hash_update_elem(), from Toke.
6) Cleanup to use BPF_PROG_RUN() macro in KCM, from Sami.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
"ctx:file_pos sysctl:read write ok" fails on s390 with "Read value !=
nux". This is because verifier rewrites a complete 32-bit
bpf_sysctl.file_pos update to a partial update of the first 32 bits of
64-bit *bpf_sysctl_kern.ppos, which is not correct on big-endian
systems.
Fix by using an offset on big-endian systems.
Ditto for bpf_sysctl.file_pos reads. Currently the test does not detect
a problem there, since it expects to see 0, which it gets with high
probability in error cases, so change it to seek to offset 3 and expect
3 in bpf_sysctl.file_pos.
Fixes: e1550bfe0d ("bpf: Add file_pos field to bpf_sysctl ctx")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20190816105300.49035-1-iii@linux.ibm.com/
Daniel Borkmann says:
====================
The following pull-request contains BPF updates for your *net-next* tree.
The main changes are:
1) Add the ability to use unaligned chunks in the AF_XDP umem. By
relaxing where the chunks can be placed, it allows to use an
arbitrary buffer size and place whenever there is a free
address in the umem. Helps more seamless DPDK AF_XDP driver
integration. Support for i40e, ixgbe and mlx5e, from Kevin and
Maxim.
2) Addition of a wakeup flag for AF_XDP tx and fill rings so the
application can wake up the kernel for rx/tx processing which
avoids busy-spinning of the latter, useful when app and driver
is located on the same core. Support for i40e, ixgbe and mlx5e,
from Magnus and Maxim.
3) bpftool fixes for printf()-like functions so compiler can actually
enforce checks, bpftool build system improvements for custom output
directories, and addition of 'bpftool map freeze' command, from Quentin.
4) Support attaching/detaching XDP programs from 'bpftool net' command,
from Daniel.
5) Automatic xskmap cleanup when AF_XDP socket is released, and several
barrier/{read,write}_once fixes in AF_XDP code, from Björn.
6) Relicense of bpf_helpers.h/bpf_endian.h for future libbpf
inclusion as well as libbpf versioning improvements, from Andrii.
7) Several new BPF kselftests for verifier precision tracking, from Alexei.
8) Several BPF kselftest fixes wrt endianess to run on s390x, from Ilya.
9) And more BPF kselftest improvements all over the place, from Stanislav.
10) Add simple BPF map op cache for nfp driver to batch dumps, from Jakub.
11) AF_XDP socket umem mapping improvements for 32bit archs, from Ivan.
12) Add BPF-to-BPF call and BTF line info support for s390x JIT, from Yauheni.
13) Small optimization in arm64 JIT to spare 1 insns for BPF_MOD, from Jerin.
14) Fix an error check in bpf_tcp_gen_syncookie() helper, from Petar.
15) Various minor fixes and cleanups, from Nathan, Masahiro, Masanari,
Peter, Wei, Yue.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
The problem can be seen in the following two tests:
0: (bf) r3 = r10
1: (55) if r3 != 0x7b goto pc+0
2: (7a) *(u64 *)(r3 -8) = 0
3: (79) r4 = *(u64 *)(r10 -8)
..
0: (85) call bpf_get_prandom_u32#7
1: (bf) r3 = r10
2: (55) if r3 != 0x7b goto pc+0
3: (7b) *(u64 *)(r3 -8) = r0
4: (79) r4 = *(u64 *)(r10 -8)
When backtracking need to mark R4 it will mark slot fp-8.
But ST or STX into fp-8 could belong to the same block of instructions.
When backtracing is done the parent state may have fp-8 slot
as "unallocated stack". Which will cause verifier to warn
and incorrectly reject such programs.
Writes into stack via non-R10 register are rare. llvm always
generates canonical stack spill/fill.
For such pathological case fall back to conservative precision
tracking instead of rejecting.
Reported-by: syzbot+c8d66267fd2b5955287e@syzkaller.appspotmail.com
Fixes: b5dc0163d8 ("bpf: precise scalar_value tracking")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Introduce BPF_F_TEST_STATE_FREQ flag to stress test parentage chain
and state pruning.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
While adding extra tests for precision tracking and extra infra
to adjust verifier heuristics the existing test
"calls: cross frame pruning - liveness propagation" started to fail.
The root cause is the same as described in verifer.c comment:
* Also if parent's curframe > frame where backtracking started,
* the verifier need to mark registers in both frames, otherwise callees
* may incorrectly prune callers. This is similar to
* commit 7640ead939 ("bpf: verifier: make sure callees don't prune with caller differences")
* For now backtracking falls back into conservative marking.
Turned out though that returning -ENOTSUPP from backtrack_insn() and
doing mark_all_scalars_precise() in the current parentage chain is not enough.
Depending on how is_state_visited() heuristic is creating parentage chain
it's possible that callee will incorrectly prune caller.
Fix the issue by setting precise=true earlier and more aggressively.
Before this fix the precision tracking _within_ functions that don't do
bpf2bpf calls would still work. Whereas now precision tracking is completely
disabled when bpf2bpf calls are present anywhere in the program.
No difference in cilium tests (they don't have bpf2bpf calls).
No difference in test_progs though some of them have bpf2bpf calls,
but precision tracking wasn't effective there.
Fixes: b5dc0163d8 ("bpf: precise scalar_value tracking")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Daniel Borkmann says:
====================
The following pull-request contains BPF updates for your *net-next* tree.
There is a small merge conflict in libbpf (Cc Andrii so he's in the loop
as well):
for (i = 1; i <= btf__get_nr_types(btf); i++) {
t = (struct btf_type *)btf__type_by_id(btf, i);
if (!has_datasec && btf_is_var(t)) {
/* replace VAR with INT */
t->info = BTF_INFO_ENC(BTF_KIND_INT, 0, 0);
<<<<<<< HEAD
/*
* using size = 1 is the safest choice, 4 will be too
* big and cause kernel BTF validation failure if
* original variable took less than 4 bytes
*/
t->size = 1;
*(int *)(t+1) = BTF_INT_ENC(0, 0, 8);
} else if (!has_datasec && kind == BTF_KIND_DATASEC) {
=======
t->size = sizeof(int);
*(int *)(t + 1) = BTF_INT_ENC(0, 0, 32);
} else if (!has_datasec && btf_is_datasec(t)) {
>>>>>>> 72ef80b5ee
/* replace DATASEC with STRUCT */
Conflict is between the two commits 1d4126c4e1 ("libbpf: sanitize VAR to
conservative 1-byte INT") and b03bc6853c ("libbpf: convert libbpf code to
use new btf helpers"), so we need to pick the sanitation fixup as well as
use the new btf_is_datasec() helper and the whitespace cleanup. Looks like
the following:
[...]
if (!has_datasec && btf_is_var(t)) {
/* replace VAR with INT */
t->info = BTF_INFO_ENC(BTF_KIND_INT, 0, 0);
/*
* using size = 1 is the safest choice, 4 will be too
* big and cause kernel BTF validation failure if
* original variable took less than 4 bytes
*/
t->size = 1;
*(int *)(t + 1) = BTF_INT_ENC(0, 0, 8);
} else if (!has_datasec && btf_is_datasec(t)) {
/* replace DATASEC with STRUCT */
[...]
The main changes are:
1) Addition of core parts of compile once - run everywhere (co-re) effort,
that is, relocation of fields offsets in libbpf as well as exposure of
kernel's own BTF via sysfs and loading through libbpf, from Andrii.
More info on co-re: http://vger.kernel.org/bpfconf2019.html#session-2
and http://vger.kernel.org/lpc-bpf2018.html#session-2
2) Enable passing input flags to the BPF flow dissector to customize parsing
and allowing it to stop early similar to the C based one, from Stanislav.
3) Add a BPF helper function that allows generating SYN cookies from XDP and
tc BPF, from Petar.
4) Add devmap hash-based map type for more flexibility in device lookup for
redirects, from Toke.
5) Improvements to XDP forwarding sample code now utilizing recently enabled
devmap lookups, from Jesper.
6) Add support for reporting the effective cgroup progs in bpftool, from Jakub
and Takshak.
7) Fix reading kernel config from bpftool via /proc/config.gz, from Peter.
8) Fix AF_XDP umem pages mapping for 32 bit architectures, from Ivan.
9) Follow-up to add two more BPF loop tests for the selftest suite, from Alexei.
10) Add perf event output helper also for other skb-based program types, from Allan.
11) Fix a co-re related compilation error in selftests, from Yonghong.
====================
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
A common pattern when using xdp_redirect_map() is to create a device map
where the lookup key is simply ifindex. Because device maps are arrays,
this leaves holes in the map, and the map has to be sized to fit the
largest ifindex, regardless of how many devices actually are actually
needed in the map.
This patch adds a second type of device map where the key is looked up
using a hashmap, instead of being used as an array index. This allows maps
to be densely packed, so they can be smaller.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The very first check in test_pkt_md_access is failing on s390, which
happens because loading a part of a struct __sk_buff field produces
an incorrect result.
The preprocessed code of the check is:
{
__u8 tmp = *((volatile __u8 *)&skb->len +
((sizeof(skb->len) - sizeof(__u8)) / sizeof(__u8)));
if (tmp != ((*(volatile __u32 *)&skb->len) & 0xFF)) return 2;
};
clang generates the following code for it:
0: 71 21 00 03 00 00 00 00 r2 = *(u8 *)(r1 + 3)
1: 61 31 00 00 00 00 00 00 r3 = *(u32 *)(r1 + 0)
2: 57 30 00 00 00 00 00 ff r3 &= 255
3: 5d 23 00 1d 00 00 00 00 if r2 != r3 goto +29 <LBB0_10>
Finally, verifier transforms it to:
0: (61) r2 = *(u32 *)(r1 +104)
1: (bc) w2 = w2
2: (74) w2 >>= 24
3: (bc) w2 = w2
4: (54) w2 &= 255
5: (bc) w2 = w2
The problem is that when verifier emits the code to replace a partial
load of a struct __sk_buff field (*(u8 *)(r1 + 3)) with a full load of
struct sk_buff field (*(u32 *)(r1 + 104)), an optional shift and a
bitwise AND, it assumes that the machine is little endian and
incorrectly decides to use a shift.
Adjust shift count calculation to account for endianness.
Fixes: 31fd85816d ("bpf: permits narrower load from bpf program context fields")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
In preparation to enabling -Wimplicit-fallthrough, this patch silences
the following warning:
kernel/bpf/verifier.c: In function ‘check_return_code’:
kernel/bpf/verifier.c:6106:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
if (env->prog->expected_attach_type == BPF_CGROUP_UDP4_RECVMSG ||
^
kernel/bpf/verifier.c:6109:2: note: here
case BPF_PROG_TYPE_CGROUP_SKB:
^~~~
Warning level 3 was used: -Wimplicit-fallthrough=3
Notice that is much clearer to explicitly add breaks in each case
statement (that actually contains some code), rather than letting
the code to fall through.
This patch is part of the ongoing efforts to enable
-Wimplicit-fallthrough.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
When backtracking instructions to propagate precision bit for registers
and stack slots, one class of instructions (BPF_ST) weren't handled
causing extra stack slots to be propagated into parent state. Parent
state might not have that much stack allocated, though, which causes
warning on invalid stack slot usage.
This patch adds handling of BPF_ST instructions:
BPF_MEM | <size> | BPF_ST: *(size *) (dst_reg + off) = imm32
Reported-by: syzbot+4da3ff23081bafe74fc2@syzkaller.appspotmail.com
Fixes: b5dc0163d8 ("bpf: precise scalar_value tracking")
Cc: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
When equivalent state is found the current state needs to propagate precision marks.
Otherwise the verifier will prune the search incorrectly.
There is a price for correctness:
before before broken fixed
cnst spill precise precise
bpf_lb-DLB_L3.o 1923 8128 1863 1898
bpf_lb-DLB_L4.o 3077 6707 2468 2666
bpf_lb-DUNKNOWN.o 1062 1062 544 544
bpf_lxc-DDROP_ALL.o 166729 380712 22629 36823
bpf_lxc-DUNKNOWN.o 174607 440652 28805 45325
bpf_netdev.o 8407 31904 6801 7002
bpf_overlay.o 5420 23569 4754 4858
bpf_lxc_jit.o 39389 359445 50925 69631
Overall precision tracking is still very effective.
Fixes: b5dc0163d8 ("bpf: precise scalar_value tracking")
Reported-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Tested-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
We don't currently allow lookups into a devmap from eBPF, because the map
lookup returns a pointer directly to the dev->ifindex, which shouldn't be
modifiable from eBPF.
However, being able to do lookups in devmaps is useful to know (e.g.)
whether forwarding to a specific interface is enabled. Currently, programs
work around this by keeping a shadow map of another type which indicates
whether a map index is valid.
Since we now have a flag to make maps read-only from the eBPF side, we can
simply lift the lookup restriction if we make sure this flag is always set.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Implement new BPF_PROG_TYPE_CGROUP_SOCKOPT program type and
BPF_CGROUP_{G,S}ETSOCKOPT cgroup hooks.
BPF_CGROUP_SETSOCKOPT can modify user setsockopt arguments before
passing them down to the kernel or bypass kernel completely.
BPF_CGROUP_GETSOCKOPT can can inspect/modify getsockopt arguments that
kernel returns.
Both hooks reuse existing PTR_TO_PACKET{,_END} infrastructure.
The buffer memory is pre-allocated (because I don't think there is
a precedent for working with __user memory from bpf). This might be
slow to do for each {s,g}etsockopt call, that's why I've added
__cgroup_bpf_prog_array_is_empty that exits early if there is nothing
attached to a cgroup. Note, however, that there is a race between
__cgroup_bpf_prog_array_is_empty and BPF_PROG_RUN_ARRAY where cgroup
program layout might have changed; this should not be a problem
because in general there is a race between multiple calls to
{s,g}etsocktop and user adding/removing bpf progs from a cgroup.
The return code of the BPF program is handled as follows:
* 0: EPERM
* 1: success, continue with next BPF program in the cgroup chain
v9:
* allow overwriting setsockopt arguments (Alexei Starovoitov):
* use set_fs (same as kernel_setsockopt)
* buffer is always kzalloc'd (no small on-stack buffer)
v8:
* use s32 for optlen (Andrii Nakryiko)
v7:
* return only 0 or 1 (Alexei Starovoitov)
* always run all progs (Alexei Starovoitov)
* use optval=0 as kernel bypass in setsockopt (Alexei Starovoitov)
(decided to use optval=-1 instead, optval=0 might be a valid input)
* call getsockopt hook after kernel handlers (Alexei Starovoitov)
v6:
* rework cgroup chaining; stop as soon as bpf program returns
0 or 2; see patch with the documentation for the details
* drop Andrii's and Martin's Acked-by (not sure they are comfortable
with the new state of things)
v5:
* skip copy_to_user() and put_user() when ret == 0 (Martin Lau)
v4:
* don't export bpf_sk_fullsock helper (Martin Lau)
* size != sizeof(__u64) for uapi pointers (Martin Lau)
* offsetof instead of bpf_ctx_range when checking ctx access (Martin Lau)
v3:
* typos in BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY comments (Andrii Nakryiko)
* reverse christmas tree in BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY (Andrii
Nakryiko)
* use __bpf_md_ptr instead of __u32 for optval{,_end} (Martin Lau)
* use BPF_FIELD_SIZEOF() for consistency (Martin Lau)
* new CG_SOCKOPT_ACCESS macro to wrap repeated parts
v2:
* moved bpf_sockopt_kern fields around to remove a hole (Martin Lau)
* aligned bpf_sockopt_kern->buf to 8 bytes (Martin Lau)
* bpf_prog_array_is_empty instead of bpf_prog_array_length (Martin Lau)
* added [0,2] return code check to verifier (Martin Lau)
* dropped unused buf[64] from the stack (Martin Lau)
* use PTR_TO_SOCKET for bpf_sockopt->sk (Martin Lau)
* dropped bpf_target_off from ctx rewrites (Martin Lau)
* use return code for kernel bypass (Martin Lau & Andrii Nakryiko)
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: Martin Lau <kafai@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Alexei Starovoitov says:
====================
pull-request: bpf-next 2019-06-19
The following pull-request contains BPF updates for your *net-next* tree.
The main changes are:
1) new SO_REUSEPORT_DETACH_BPF setsocktopt, from Martin.
2) BTF based map definition, from Andrii.
3) support bpf_map_lookup_elem for xskmap, from Jonathan.
4) bounded loops and scalar precision logic in the verifier, from Alexei.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Introduce precision tracking logic that
helps cilium programs the most:
old clang old clang new clang new clang
with all patches with all patches
bpf_lb-DLB_L3.o 1838 2283 1923 1863
bpf_lb-DLB_L4.o 3218 2657 3077 2468
bpf_lb-DUNKNOWN.o 1064 545 1062 544
bpf_lxc-DDROP_ALL.o 26935 23045 166729 22629
bpf_lxc-DUNKNOWN.o 34439 35240 174607 28805
bpf_netdev.o 9721 8753 8407 6801
bpf_overlay.o 6184 7901 5420 4754
bpf_lxc_jit.o 39389 50925 39389 50925
Consider code:
654: (85) call bpf_get_hash_recalc#34
655: (bf) r7 = r0
656: (15) if r8 == 0x0 goto pc+29
657: (bf) r2 = r10
658: (07) r2 += -48
659: (18) r1 = 0xffff8881e41e1b00
661: (85) call bpf_map_lookup_elem#1
662: (15) if r0 == 0x0 goto pc+23
663: (69) r1 = *(u16 *)(r0 +0)
664: (15) if r1 == 0x0 goto pc+21
665: (bf) r8 = r7
666: (57) r8 &= 65535
667: (bf) r2 = r8
668: (3f) r2 /= r1
669: (2f) r2 *= r1
670: (bf) r1 = r8
671: (1f) r1 -= r2
672: (57) r1 &= 255
673: (25) if r1 > 0x1e goto pc+12
R0=map_value(id=0,off=0,ks=20,vs=64,imm=0) R1_w=inv(id=0,umax_value=30,var_off=(0x0; 0x1f))
674: (67) r1 <<= 1
675: (0f) r0 += r1
At this point the verifier will notice that scalar R1 is used in map pointer adjustment.
R1 has to be precise for later operations on R0 to be validated properly.
The verifier will backtrack the above code in the following way:
last_idx 675 first_idx 664
regs=2 stack=0 before 675: (0f) r0 += r1 // started backtracking R1 regs=2 is a bitmask
regs=2 stack=0 before 674: (67) r1 <<= 1
regs=2 stack=0 before 673: (25) if r1 > 0x1e goto pc+12
regs=2 stack=0 before 672: (57) r1 &= 255
regs=2 stack=0 before 671: (1f) r1 -= r2 // now both R1 and R2 has to be precise -> regs=6 mask
regs=6 stack=0 before 670: (bf) r1 = r8 // after this insn R8 and R2 has to be precise
regs=104 stack=0 before 669: (2f) r2 *= r1 // after this one R8, R2, and R1
regs=106 stack=0 before 668: (3f) r2 /= r1
regs=106 stack=0 before 667: (bf) r2 = r8
regs=102 stack=0 before 666: (57) r8 &= 65535
regs=102 stack=0 before 665: (bf) r8 = r7
regs=82 stack=0 before 664: (15) if r1 == 0x0 goto pc+21
// this is the end of verifier state. The following regs will be marked precised:
R1_rw=invP(id=0,umax_value=65535,var_off=(0x0; 0xffff)) R7_rw=invP(id=0)
parent didn't have regs=82 stack=0 marks // so backtracking continues into parent state
last_idx 663 first_idx 655
regs=82 stack=0 before 663: (69) r1 = *(u16 *)(r0 +0) // R1 was assigned no need to track it further
regs=80 stack=0 before 662: (15) if r0 == 0x0 goto pc+23 // keep tracking R7
regs=80 stack=0 before 661: (85) call bpf_map_lookup_elem#1 // keep tracking R7
regs=80 stack=0 before 659: (18) r1 = 0xffff8881e41e1b00
regs=80 stack=0 before 658: (07) r2 += -48
regs=80 stack=0 before 657: (bf) r2 = r10
regs=80 stack=0 before 656: (15) if r8 == 0x0 goto pc+29
regs=80 stack=0 before 655: (bf) r7 = r0 // here the assignment into R7
// mark R0 to be precise:
R0_rw=invP(id=0)
parent didn't have regs=1 stack=0 marks // regs=1 -> tracking R0
last_idx 654 first_idx 644
regs=1 stack=0 before 654: (85) call bpf_get_hash_recalc#34 // and in the parent frame it was a return value
// nothing further to backtrack
Two scalar registers not marked precise are equivalent from state pruning point of view.
More details in the patch comments.
It doesn't support bpf2bpf calls yet and enabled for root only.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
The commit 7640ead939 partially resolved the issue of callees
incorrectly pruning the callers.
With introduction of bounded loops and jmps_processed heuristic
single verifier state may contain multiple branches and calls.
It's possible that new verifier state (for future pruning) will be
allocated inside callee. Then callee will exit (still within the same
verifier state). It will go back to the caller and there R6-R9 registers
will be read and will trigger mark_reg_read. But the reg->live for all frames
but the top frame is not set to LIVE_NONE. Hence mark_reg_read will fail
to propagate liveness into parent and future walking will incorrectly
conclude that the states are equivalent because LIVE_READ is not set.
In other words the rule for parent/live should be:
whenever register parentage chain is set the reg->live should be set to LIVE_NONE.
is_state_visited logic already follows this rule for spilled registers.
Fixes: 7640ead939 ("bpf: verifier: make sure callees don't prune with caller differences")
Fixes: f4d7e40a5b ("bpf: introduce function calls (verification)")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Allow the verifier to validate the loops by simulating their execution.
Exisiting programs have used '#pragma unroll' to unroll the loops
by the compiler. Instead let the verifier simulate all iterations
of the loop.
In order to do that introduce parentage chain of bpf_verifier_state and
'branches' counter for the number of branches left to explore.
See more detailed algorithm description in bpf_verifier.h
This algorithm borrows the key idea from Edward Cree approach:
https://patchwork.ozlabs.org/patch/877222/
Additional state pruning heuristics make such brute force loop walk
practical even for large loops.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This patch extends is_branch_taken() logic from JMP+K instructions
to JMP+X instructions.
Conditional branches are often done when src and dst registers
contain known scalars. In such case the verifier can follow
the branch that is going to be taken when program executes.
That speeds up the verification and is essential feature to support
bounded loops.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Compilers often spill induction variables into the stack,
hence it is necessary for the verifier to track scalar values
of the registers through stack slots.
Also few bpf programs were incorrectly rejected in the past,
since the verifier was not able to track such constants while
they were used to compute offsets into packet headers.
Tracking constants through the stack significantly decreases
the chances of state pruning, since two different constants
are considered to be different by state equivalency.
End result that cilium tests suffer serious degradation in the number
of states processed and corresponding verification time increase.
before after
bpf_lb-DLB_L3.o 1838 6441
bpf_lb-DLB_L4.o 3218 5908
bpf_lb-DUNKNOWN.o 1064 1064
bpf_lxc-DDROP_ALL.o 26935 93790
bpf_lxc-DUNKNOWN.o 34439 123886
bpf_netdev.o 9721 31413
bpf_overlay.o 6184 18561
bpf_lxc_jit.o 39389 359445
After further debugging turned out that cillium progs are
getting hurt by clang due to the same constant tracking issue.
Newer clang generates better code by spilling less to the stack.
Instead it keeps more constants in the registers which
hurts state pruning since the verifier already tracks constants
in the registers:
old clang new clang
(no spill/fill tracking introduced by this patch)
bpf_lb-DLB_L3.o 1838 1923
bpf_lb-DLB_L4.o 3218 3077
bpf_lb-DUNKNOWN.o 1064 1062
bpf_lxc-DDROP_ALL.o 26935 166729
bpf_lxc-DUNKNOWN.o 34439 174607
bpf_netdev.o 9721 8407
bpf_overlay.o 6184 5420
bpf_lcx_jit.o 39389 39389
The final table is depressing:
old clang old clang new clang new clang
const spill/fill const spill/fill
bpf_lb-DLB_L3.o 1838 6441 1923 8128
bpf_lb-DLB_L4.o 3218 5908 3077 6707
bpf_lb-DUNKNOWN.o 1064 1064 1062 1062
bpf_lxc-DDROP_ALL.o 26935 93790 166729 380712
bpf_lxc-DUNKNOWN.o 34439 123886 174607 440652
bpf_netdev.o 9721 31413 8407 31904
bpf_overlay.o 6184 18561 5420 23569
bpf_lxc_jit.o 39389 359445 39389 359445
Tracking constants in the registers hurts state pruning already.
Adding tracking of constants through stack hurts pruning even more.
The later patch address this general constant tracking issue
with coarse/precise logic.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Pull networking fixes from David Miller:
"Lots of bug fixes here:
1) Out of bounds access in __bpf_skc_lookup, from Lorenz Bauer.
2) Fix rate reporting in cfg80211_calculate_bitrate_he(), from John
Crispin.
3) Use after free in psock backlog workqueue, from John Fastabend.
4) Fix source port matching in fdb peer flow rule of mlx5, from Raed
Salem.
5) Use atomic_inc_not_zero() in fl6_sock_lookup(), from Eric Dumazet.
6) Network header needs to be set for packet redirect in nfp, from
John Hurley.
7) Fix udp zerocopy refcnt, from Willem de Bruijn.
8) Don't assume linear buffers in vxlan and geneve error handlers,
from Stefano Brivio.
9) Fix TOS matching in mlxsw, from Jiri Pirko.
10) More SCTP cookie memory leak fixes, from Neil Horman.
11) Fix VLAN filtering in rtl8366, from Linus Walluij.
12) Various TCP SACK payload size and fragmentation memory limit fixes
from Eric Dumazet.
13) Use after free in pneigh_get_next(), also from Eric Dumazet.
14) LAPB control block leak fix from Jeremy Sowden"
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (145 commits)
lapb: fixed leak of control-blocks.
tipc: purge deferredq list for each grp member in tipc_group_delete
ax25: fix inconsistent lock state in ax25_destroy_timer
neigh: fix use-after-free read in pneigh_get_next
tcp: fix compile error if !CONFIG_SYSCTL
hv_sock: Suppress bogus "may be used uninitialized" warnings
be2net: Fix number of Rx queues used for flow hashing
net: handle 802.1P vlan 0 packets properly
tcp: enforce tcp_min_snd_mss in tcp_mtu_probing()
tcp: add tcp_min_snd_mss sysctl
tcp: tcp_fragment() should apply sane memory limits
tcp: limit payload size of sacked skbs
Revert "net: phylink: set the autoneg state in phylink_phy_change"
bpf: fix nested bpf tracepoints with per-cpu data
bpf: Fix out of bounds memory access in bpf_sk_storage
vsock/virtio: set SOCK_DONE on peer shutdown
net: dsa: rtl8366: Fix up VLAN filtering
net: phylink: set the autoneg state in phylink_phy_change
net: add high_order_alloc_disable sysctl/static key
tcp: add tcp_tx_skb_cache sysctl
...
Currently, the AF_XDP code uses a separate map in order to
determine if an xsk is bound to a queue. Instead of doing this,
have bpf_map_lookup_elem() return a xdp_sock.
Rearrange some xdp_sock members to eliminate structure holes.
Remove selftest - will be added back in later patch.
Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Intention of cgroup bind/connect/sendmsg BPF hooks is to act transparently
to applications as also stated in original motivation in 7828f20e37 ("Merge
branch 'bpf-cgroup-bind-connect'"). When recently integrating the latter
two hooks into Cilium to enable host based load-balancing with Kubernetes,
I ran into the issue that pods couldn't start up as DNS got broken. Kubernetes
typically sets up DNS as a service and is thus subject to load-balancing.
Upon further debugging, it turns out that the cgroupv2 sendmsg BPF hooks API
is currently insufficient and thus not usable as-is for standard applications
shipped with most distros. To break down the issue we ran into with a simple
example:
# cat /etc/resolv.conf
nameserver 147.75.207.207
nameserver 147.75.207.208
For the purpose of a simple test, we set up above IPs as service IPs and
transparently redirect traffic to a different DNS backend server for that
node:
# cilium service list
ID Frontend Backend
1 147.75.207.207:53 1 => 8.8.8.8:53
2 147.75.207.208:53 1 => 8.8.8.8:53
The attached BPF program is basically selecting one of the backends if the
service IP/port matches on the cgroup hook. DNS breaks here, because the
hooks are not transparent enough to applications which have built-in msg_name
address checks:
# nslookup 1.1.1.1
;; reply from unexpected source: 8.8.8.8#53, expected 147.75.207.207#53
;; reply from unexpected source: 8.8.8.8#53, expected 147.75.207.208#53
;; reply from unexpected source: 8.8.8.8#53, expected 147.75.207.207#53
[...]
;; connection timed out; no servers could be reached
# dig 1.1.1.1
;; reply from unexpected source: 8.8.8.8#53, expected 147.75.207.207#53
;; reply from unexpected source: 8.8.8.8#53, expected 147.75.207.208#53
;; reply from unexpected source: 8.8.8.8#53, expected 147.75.207.207#53
[...]
; <<>> DiG 9.11.3-1ubuntu1.7-Ubuntu <<>> 1.1.1.1
;; global options: +cmd
;; connection timed out; no servers could be reached
For comparison, if none of the service IPs is used, and we tell nslookup
to use 8.8.8.8 directly it works just fine, of course:
# nslookup 1.1.1.1 8.8.8.8
1.1.1.1.in-addr.arpa name = one.one.one.one.
In order to fix this and thus act more transparent to the application,
this needs reverse translation on recvmsg() side. A minimal fix for this
API is to add similar recvmsg() hooks behind the BPF cgroups static key
such that the program can track state and replace the current sockaddr_in{,6}
with the original service IP. From BPF side, this basically tracks the
service tuple plus socket cookie in an LRU map where the reverse NAT can
then be retrieved via map value as one example. Side-note: the BPF cgroups
static key should be converted to a per-hook static key in future.
Same example after this fix:
# cilium service list
ID Frontend Backend
1 147.75.207.207:53 1 => 8.8.8.8:53
2 147.75.207.208:53 1 => 8.8.8.8:53
Lookups work fine now:
# nslookup 1.1.1.1
1.1.1.1.in-addr.arpa name = one.one.one.one.
Authoritative answers can be found from:
# dig 1.1.1.1
; <<>> DiG 9.11.3-1ubuntu1.7-Ubuntu <<>> 1.1.1.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 51550
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;1.1.1.1. IN A
;; AUTHORITY SECTION:
. 23426 IN SOA a.root-servers.net. nstld.verisign-grs.com. 2019052001 1800 900 604800 86400
;; Query time: 17 msec
;; SERVER: 147.75.207.207#53(147.75.207.207)
;; WHEN: Tue May 21 12:59:38 UTC 2019
;; MSG SIZE rcvd: 111
And from an actual packet level it shows that we're using the back end
server when talking via 147.75.207.20{7,8} front end:
# tcpdump -i any udp
[...]
12:59:52.698732 IP foo.42011 > google-public-dns-a.google.com.domain: 18803+ PTR? 1.1.1.1.in-addr.arpa. (38)
12:59:52.698735 IP foo.42011 > google-public-dns-a.google.com.domain: 18803+ PTR? 1.1.1.1.in-addr.arpa. (38)
12:59:52.701208 IP google-public-dns-a.google.com.domain > foo.42011: 18803 1/0/0 PTR one.one.one.one. (67)
12:59:52.701208 IP google-public-dns-a.google.com.domain > foo.42011: 18803 1/0/0 PTR one.one.one.one. (67)
[...]
In order to be flexible and to have same semantics as in sendmsg BPF
programs, we only allow return codes in [1,1] range. In the sendmsg case
the program is called if msg->msg_name is present which can be the case
in both, connected and unconnected UDP.
The former only relies on the sockaddr_in{,6} passed via connect(2) if
passed msg->msg_name was NULL. Therefore, on recvmsg side, we act in similar
way to call into the BPF program whenever a non-NULL msg->msg_name was
passed independent of sk->sk_state being TCP_ESTABLISHED or not. Note
that for TCP case, the msg->msg_name is ignored in the regular recvmsg
path and therefore not relevant.
For the case of ip{,v6}_recv_error() paths, picked up via MSG_ERRQUEUE,
the hook is not called. This is intentional as it aligns with the same
semantics as in case of TCP cgroup BPF hooks right now. This might be
better addressed in future through a different bpf_attach_type such
that this case can be distinguished from the regular recvmsg paths,
for example.
Fixes: 1cedee13d2 ("bpf: Hooks for sys_sendmsg")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrey Ignatov <rdna@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Martynas Pumputis <m@lambda.lt>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of version 2 of the gnu general public license as
published by the free software foundation this program is
distributed in the hope that it will be useful but without any
warranty without even the implied warranty of merchantability or
fitness for a particular purpose see the gnu general public license
for more details
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 64 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190529141901.894819585@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Allows cgroup inet skb programs to return values in the range [0, 3].
The second bit is used to deterine if congestion occurred and higher
level protocol should decrease rate. E.g. TCP would call tcp_enter_cwr()
The bpf_prog must set expected_attach_type to BPF_CGROUP_INET_EGRESS
at load time if it uses the new return values (i.e. 2 or 3).
The expected_attach_type is currently not enforced for
BPF_PROG_TYPE_CGROUP_SKB. e.g Meaning the current bpf_prog with
expected_attach_type setting to BPF_CGROUP_INET_EGRESS can attach to
BPF_CGROUP_INET_INGRESS. Blindly enforcing expected_attach_type will
break backward compatibility.
This patch adds a enforce_expected_attach_type bit to only
enforce the expected_attach_type when it uses the new
return value.
Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This patch randomizes high 32-bit of a definition when BPF_F_TEST_RND_HI32
is set.
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
After previous patches, verifier will mark a insn if it really needs zero
extension on dst_reg.
It is then for back-ends to decide how to use such information to eliminate
unnecessary zero extension code-gen during JIT compilation.
One approach is verifier insert explicit zero extension for those insns
that need zero extension in a generic way, JIT back-ends then do not
generate zero extension for sub-register write at default.
However, only those back-ends which do not have hardware zero extension
want this optimization. Back-ends like x86_64 and AArch64 have hardware
zero extension support that the insertion should be disabled.
This patch introduces new target hook "bpf_jit_needs_zext" which returns
false at default, meaning verifier zero extension insertion is disabled at
default. A back-end could override this hook to return true if it doesn't
have hardware support and want verifier insert zero extension explicitly.
Offload targets do not use this native target hook, instead, they could
get the optimization results using bpf_prog_offload_ops.finalize.
NOTE: arches could have diversified features, it is possible for one arch
to have hardware zero extension support for some sub-register write insns
but not for all. For example, PowerPC, SPARC have zero extended loads, but
not for alu32. So when verifier zero extension insertion enabled, these JIT
back-ends need to peephole insns to remove those zero extension inserted
for insn that actually has hardware zero extension support. The peephole
could be as simple as looking the next insn, if it is a special zero
extension insn then it is safe to eliminate it if the current insn has
hardware zero extension support.
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Patched insns do not go through generic verification, therefore doesn't has
zero extension information collected during insn walking.
We don't bother analyze them at the moment, for any sub-register def comes
from them, just conservatively mark it as needing zero extension.
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
eBPF ISA specification requires high 32-bit cleared when low 32-bit
sub-register is written. This applies to destination register of ALU32 etc.
JIT back-ends must guarantee this semantic when doing code-gen. x86_64 and
AArch64 ISA has the same semantics, so the corresponding JIT back-end
doesn't need to do extra work.
However, 32-bit arches (arm, x86, nfp etc.) and some other 64-bit arches
(PowerPC, SPARC etc) need to do explicit zero extension to meet this
requirement, otherwise code like the following will fail.
u64_value = (u64) u32_value
... other uses of u64_value
This is because compiler could exploit the semantic described above and
save those zero extensions for extending u32_value to u64_value, these JIT
back-ends are expected to guarantee this through inserting extra zero
extensions which however could be a significant increase on the code size.
Some benchmarks show there could be ~40% sub-register writes out of total
insns, meaning at least ~40% extra code-gen.
One observation is these extra zero extensions are not always necessary.
Take above code snippet for example, it is possible u32_value will never be
casted into a u64, the value of high 32-bit of u32_value then could be
ignored and extra zero extension could be eliminated.
This patch implements this idea, insns defining sub-registers will be
marked when the high 32-bit of the defined sub-register matters. For
those unmarked insns, it is safe to eliminate high 32-bit clearnace for
them.
Algo:
- Split read flags into READ32 and READ64.
- Record index of insn that does sub-register write. Keep the index inside
reg state and update it during verifier insn walking.
- A full register read on a sub-register marks its definition insn as
needing zero extension on dst register.
A new sub-register write overrides the old one.
- When propagating read64 during path pruning, also mark any insn defining
a sub-register that is read in the pruned path as full-register.
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
All prune points inside a callee bpf function most likely will have
different callsites. For example, if function foo() is called from
two callsites the half of explored states in all prune points in foo()
will be useless for subsequent walking of one of those callsites.
Fortunately explored_states pruning heuristics keeps the number of states
per prune point small, but walking these states is still a waste of cpu
time when the callsite of the current state is different from the callsite
of the explored state.
To improve pruning logic convert explored_states into hash table and
use simple insn_idx ^ callsite hash to select hash bucket.
This optimization has no effect on programs without bpf2bpf calls
and drastically improves programs with calls.
In the later case it reduces total memory consumption in 1M scale tests
by almost 3 times (peak_states drops from 5752 to 2016).
Care should be taken when comparing the states for equivalency.
Since the same hash bucket can now contain states with different indices
the insn_idx has to be part of verifier_state and compared.
Different hash table sizes and different hash functions were explored,
but the results were not significantly better vs this patch.
They can be improved in the future.
Hit/miss heuristic is not counting index miscompare as a miss.
Otherwise verifier stats become unstable when experimenting
with different hash functions.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
split explored_states into prune_point boolean mark
and link list of explored states.
This removes STATE_LIST_MARK hack and allows marks to be separate from states.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
clean up explored_states to prep for introduction of hashtable
No functional changes.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
The limit of 1024 subsequent jumps was causing otherwise valid
programs to be rejected. Bump it to 8192 and make the error more verbose.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Commit 31fd85816d ("bpf: permits narrower load from bpf program
context fields") made the verifier add AND instructions to clear the
unwanted bits with a mask when doing a narrow load. The mask is
computed with
(1 << size * 8) - 1
where "size" is the size of the narrow load. When doing a 4 byte load
of a an 8 byte field the verifier shifts the literal 1 by 32 places to
the left. This results in an overflow of a signed integer, which is an
undefined behavior. Typically, the computed mask was zero, so the
result of the narrow load ended up being zero too.
Cast the literal to long long to avoid overflows. Note that narrow
load of the 4 byte fields does not have the undefined behavior,
because the load size can only be either 1 or 2 bytes, so shifting 1
by 8 or 16 places will not overflow it. And reading 4 bytes would not
be a narrow load of a 4 bytes field.
Fixes: 31fd85816d ("bpf: permits narrower load from bpf program context fields")
Reviewed-by: Alban Crequy <alban@kinvolk.io>
Reviewed-by: Iago López Galeiras <iago@kinvolk.io>
Signed-off-by: Krzesimir Nowak <krzesimir@kinvolk.io>
Cc: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
After allowing a bpf prog to
- directly read the skb->sk ptr
- get the fullsock bpf_sock by "bpf_sk_fullsock()"
- get the bpf_tcp_sock by "bpf_tcp_sock()"
- get the listener sock by "bpf_get_listener_sock()"
- avoid duplicating the fields of "(bpf_)sock" and "(bpf_)tcp_sock"
into different bpf running context.
this patch is another effort to make bpf's network programming
more intuitive to do (together with memory and performance benefit).
When bpf prog needs to store data for a sk, the current practice is to
define a map with the usual 4-tuples (src/dst ip/port) as the key.
If multiple bpf progs require to store different sk data, multiple maps
have to be defined. Hence, wasting memory to store the duplicated
keys (i.e. 4 tuples here) in each of the bpf map.
[ The smallest key could be the sk pointer itself which requires
some enhancement in the verifier and it is a separate topic. ]
Also, the bpf prog needs to clean up the elem when sk is freed.
Otherwise, the bpf map will become full and un-usable quickly.
The sk-free tracking currently could be done during sk state
transition (e.g. BPF_SOCK_OPS_STATE_CB).
The size of the map needs to be predefined which then usually ended-up
with an over-provisioned map in production. Even the map was re-sizable,
while the sk naturally come and go away already, this potential re-size
operation is arguably redundant if the data can be directly connected
to the sk itself instead of proxy-ing through a bpf map.
This patch introduces sk->sk_bpf_storage to provide local storage space
at sk for bpf prog to use. The space will be allocated when the first bpf
prog has created data for this particular sk.
The design optimizes the bpf prog's lookup (and then optionally followed by
an inline update). bpf_spin_lock should be used if the inline update needs
to be protected.
BPF_MAP_TYPE_SK_STORAGE:
-----------------------
To define a bpf "sk-local-storage", a BPF_MAP_TYPE_SK_STORAGE map (new in
this patch) needs to be created. Multiple BPF_MAP_TYPE_SK_STORAGE maps can
be created to fit different bpf progs' needs. The map enforces
BTF to allow printing the sk-local-storage during a system-wise
sk dump (e.g. "ss -ta") in the future.
The purpose of a BPF_MAP_TYPE_SK_STORAGE map is not for lookup/update/delete
a "sk-local-storage" data from a particular sk.
Think of the map as a meta-data (or "type") of a "sk-local-storage". This
particular "type" of "sk-local-storage" data can then be stored in any sk.
The main purposes of this map are mostly:
1. Define the size of a "sk-local-storage" type.
2. Provide a similar syscall userspace API as the map (e.g. lookup/update,
map-id, map-btf...etc.)
3. Keep track of all sk's storages of this "type" and clean them up
when the map is freed.
sk->sk_bpf_storage:
------------------
The main lookup/update/delete is done on sk->sk_bpf_storage (which
is a "struct bpf_sk_storage"). When doing a lookup,
the "map" pointer is now used as the "key" to search on the
sk_storage->list. The "map" pointer is actually serving
as the "type" of the "sk-local-storage" that is being
requested.
To allow very fast lookup, it should be as fast as looking up an
array at a stable-offset. At the same time, it is not ideal to
set a hard limit on the number of sk-local-storage "type" that the
system can have. Hence, this patch takes a cache approach.
The last search result from sk_storage->list is cached in
sk_storage->cache[] which is a stable sized array. Each
"sk-local-storage" type has a stable offset to the cache[] array.
In the future, a map's flag could be introduced to do cache
opt-out/enforcement if it became necessary.
The cache size is 16 (i.e. 16 types of "sk-local-storage").
Programs can share map. On the program side, having a few bpf_progs
running in the networking hotpath is already a lot. The bpf_prog
should have already consolidated the existing sock-key-ed map usage
to minimize the map lookup penalty. 16 has enough runway to grow.
All sk-local-storage data will be removed from sk->sk_bpf_storage
during sk destruction.
bpf_sk_storage_get() and bpf_sk_storage_delete():
------------------------------------------------
Instead of using bpf_map_(lookup|update|delete)_elem(),
the bpf prog needs to use the new helper bpf_sk_storage_get() and
bpf_sk_storage_delete(). The verifier can then enforce the
ARG_PTR_TO_SOCKET argument. The bpf_sk_storage_get() also allows to
"create" new elem if one does not exist in the sk. It is done by
the new BPF_SK_STORAGE_GET_F_CREATE flag. An optional value can also be
provided as the initial value during BPF_SK_STORAGE_GET_F_CREATE.
The BPF_MAP_TYPE_SK_STORAGE also supports bpf_spin_lock. Together,
it has eliminated the potential use cases for an equivalent
bpf_map_update_elem() API (for bpf_prog) in this patch.
Misc notes:
----------
1. map_get_next_key is not supported. From the userspace syscall
perspective, the map has the socket fd as the key while the map
can be shared by pinned-file or map-id.
Since btf is enforced, the existing "ss" could be enhanced to pretty
print the local-storage.
Supporting a kernel defined btf with 4 tuples as the return key could
be explored later also.
2. The sk->sk_lock cannot be acquired. Atomic operations is used instead.
e.g. cmpxchg is done on the sk->sk_bpf_storage ptr.
Please refer to the source code comments for the details in
synchronization cases and considerations.
3. The mem is charged to the sk->sk_omem_alloc as the sk filter does.
Benchmark:
---------
Here is the benchmark data collected by turning on
the "kernel.bpf_stats_enabled" sysctl.
Two bpf progs are tested:
One bpf prog with the usual bpf hashmap (max_entries = 8192) with the
sk ptr as the key. (verifier is modified to support sk ptr as the key
That should have shortened the key lookup time.)
Another bpf prog is with the new BPF_MAP_TYPE_SK_STORAGE.
Both are storing a "u32 cnt", do a lookup on "egress_skb/cgroup" for
each egress skb and then bump the cnt. netperf is used to drive
data with 4096 connected UDP sockets.
BPF_MAP_TYPE_HASH with a modifier verifier (152ns per bpf run)
27: cgroup_skb name egress_sk_map tag 74f56e832918070b run_time_ns 58280107540 run_cnt 381347633
loaded_at 2019-04-15T13:46:39-0700 uid 0
xlated 344B jited 258B memlock 4096B map_ids 16
btf_id 5
BPF_MAP_TYPE_SK_STORAGE in this patch (66ns per bpf run)
30: cgroup_skb name egress_sk_stora tag d4aa70984cc7bbf6 run_time_ns 25617093319 run_cnt 390989739
loaded_at 2019-04-15T13:47:54-0700 uid 0
xlated 168B jited 156B memlock 4096B map_ids 17
btf_id 6
Here is a high-level picture on how are the objects organized:
sk
┌──────┐
│ │
│ │
│ │
│*sk_bpf_storage─────▶ bpf_sk_storage
└──────┘ ┌───────┐
┌───────────┤ list │
│ │ │
│ │ │
│ │ │
│ └───────┘
│
│ elem
│ ┌────────┐
├─▶│ snode │
│ ├────────┤
│ │ data │ bpf_map
│ ├────────┤ ┌─────────┐
│ │map_node│◀─┬─────┤ list │
│ └────────┘ │ │ │
│ │ │ │
│ elem │ │ │
│ ┌────────┐ │ └─────────┘
└─▶│ snode │ │
├────────┤ │
bpf_map │ data │ │
┌─────────┐ ├────────┤ │
│ list ├───────▶│map_node│ │
│ │ └────────┘ │
│ │ │
│ │ elem │
└─────────┘ ┌────────┐ │
┌─▶│ snode │ │
│ ├────────┤ │
│ │ data │ │
│ ├────────┤ │
│ │map_node│◀─┘
│ └────────┘
│
│
│ ┌───────┐
sk └──────────│ list │
┌──────┐ │ │
│ │ │ │
│ │ │ │
│ │ └───────┘
│*sk_bpf_storage───────▶bpf_sk_storage
└──────┘
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This is an opt-in interface that allows a tracepoint to provide a safe
buffer that can be written from a BPF_PROG_TYPE_RAW_TRACEPOINT program.
The size of the buffer must be a compile-time constant, and is checked
before allowing a BPF program to attach to a tracepoint that uses this
feature.
The pointer to this buffer will be the first argument of tracepoints
that opt in; the pointer is valid and can be bpf_probe_read() by both
BPF_PROG_TYPE_RAW_TRACEPOINT and BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE
programs that attach to such a tracepoint, but the buffer to which it
points may only be written by the latter.
Signed-off-by: Matt Mullins <mmullins@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
In case of a null check on a pointer inside a subprog, we should mark all
registers with this pointer as either safe or unknown, in both the current
and previous frames. Currently, only spilled registers and registers in
the current frame are marked. Packet bound checks in subprogs have the
same issue. This patch fixes it to mark registers in previous frames as
well.
A good reproducer for null checks looks as follow:
1: ptr = bpf_map_lookup_elem(map, &key);
2: ret = subprog(ptr) {
3: return ptr != NULL;
4: }
5: if (ret)
6: value = *ptr;
With the above, the verifier will complain on line 6 because it sees ptr
as map_value_or_null despite the null check in subprog 1.
Note that this patch fixes another resulting bug when using
bpf_sk_release():
1: sk = bpf_sk_lookup_tcp(...);
2: subprog(sk) {
3: if (sk)
4: bpf_sk_release(sk);
5: }
6: if (!sk)
7: return 0;
8: return 1;
In the above, mark_ptr_or_null_regs will warn on line 6 because it will
try to free the reference state, even though it was already freed on
line 3.
Fixes: f4d7e40a5b ("bpf: introduce function calls (verification)")
Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Drop bpf_verifier_lock for root to avoid being DoS-ed by unprivileged.
The BPF verifier is now fully parallel.
All unpriv users are still serialized by bpf_verifier_lock to avoid
exhausting kernel memory by running N parallel verifications.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Move three global variables protected by bpf_verifier_lock into
'struct bpf_verifier_env' to allow parallel verification.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
verifier.c uses BPF_CAST_CALL for casting bpf call except at one
place in jit_subprogs(). Let's use the macro for consistency.
Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
There are a few "regs[regno]" here are there across "check_reg_arg", this
patch factor it out into a simple "reg" pointer. The intention is to
simplify code indentation and make the later patches in this set look
cleaner.
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
After code refactor in previous patches, the propagation logic inside the
for loop in "propagate_liveness" becomes clear that they are good enough to
be factored out into a common function "propagate_liveness_reg".
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Access to reg states were not factored out, the consequence is long code
for dereferencing them which made the indentation not good for reading.
This patch factor out these code so the core code in the loop could be
easier to follow.
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Propagation for register and stack slot are finished in separate for loop,
while they are perfect to be put into a single loop.
This could also let them share some common variables in later patches.
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Currently the way to pass result from BPF helper to BPF program is to
provide memory area defined by pointer and size: func(void *, size_t).
It works great for generic use-case, but for simple types, such as int,
it's overkill and consumes two arguments when it could use just one.
Introduce new argument types ARG_PTR_TO_INT and ARG_PTR_TO_LONG to be
able to pass result from helper to program via pointer to int and long
correspondingly: func(int *) or func(long *).
New argument types are similar to ARG_PTR_TO_MEM with the following
differences:
* they don't require corresponding ARG_CONST_SIZE argument, predefined
access sizes are used instead (32bit for int, 64bit for long);
* it's possible to use more than one such an argument in a helper;
* provided pointers have to be aligned.
It's easy to introduce similar ARG_PTR_TO_CHAR and ARG_PTR_TO_SHORT
argument types. It's not done due to lack of use-case though.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Containerized applications may run as root and it may create problems
for whole host. Specifically such applications may change a sysctl and
affect applications in other containers.
Furthermore in existing infrastructure it may not be possible to just
completely disable writing to sysctl, instead such a process should be
gradual with ability to log what sysctl are being changed by a
container, investigate, limit the set of writable sysctl to currently
used ones (so that new ones can not be changed) and eventually reduce
this set to zero.
The patch introduces new program type BPF_PROG_TYPE_CGROUP_SYSCTL and
attach type BPF_CGROUP_SYSCTL to solve these problems on cgroup basis.
New program type has access to following minimal context:
struct bpf_sysctl {
__u32 write;
};
Where @write indicates whether sysctl is being read (= 0) or written (=
1).
Helpers to access sysctl name and value will be introduced separately.
BPF_CGROUP_SYSCTL attach point is added to sysctl code right before
passing control to ctl_table->proc_handler so that BPF program can
either allow or deny access to sysctl.
Suggested-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Daniel Borkmann says:
====================
pull-request: bpf-next 2019-04-12
The following pull-request contains BPF updates for your *net-next* tree.
The main changes are:
1) Improve BPF verifier scalability for large programs through two
optimizations: i) remove verifier states that are not useful in pruning,
ii) stop walking parentage chain once first LIVE_READ is seen. Combined
gives approx 20x speedup. Increase limits for accepting large programs
under root, and add various stress tests, from Alexei.
2) Implement global data support in BPF. This enables static global variables
for .data, .rodata and .bss sections to be properly handled which allows
for more natural program development. This also opens up the possibility
to optimize program workflow by compiling ELFs only once and later only
rewriting section data before reload, from Daniel and with test cases and
libbpf refactoring from Joe.
3) Add config option to generate BTF type info for vmlinux as part of the
kernel build process. DWARF debug info is converted via pahole to BTF.
Latter relies on libbpf and makes use of BTF deduplication algorithm which
results in 100x savings compared to DWARF data. Resulting .BTF section is
typically about 2MB in size, from Andrii.
4) Add BPF verifier support for stack access with variable offset from
helpers and add various test cases along with it, from Andrey.
5) Extend bpf_skb_adjust_room() growth BPF helper to mark inner MAC header
so that L2 encapsulation can be used for tc tunnels, from Alan.
6) Add support for input __sk_buff context in BPF_PROG_TEST_RUN so that
users can define a subset of allowed __sk_buff fields that get fed into
the test program, from Stanislav.
7) Add bpf fs multi-dimensional array tests for BTF test suite and fix up
various UBSAN warnings in bpftool, from Yonghong.
8) Generate a pkg-config file for libbpf, from Luca.
9) Dump program's BTF id in bpftool, from Prashant.
10) libbpf fix to use smaller BPF log buffer size for AF_XDP's XDP
program, from Magnus.
11) kallsyms related fixes for the case when symbols are not present in
BPF selftests and samples, from Daniel
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
This work adds two new map creation flags BPF_F_RDONLY_PROG
and BPF_F_WRONLY_PROG in order to allow for read-only or
write-only BPF maps from a BPF program side.
Today we have BPF_F_RDONLY and BPF_F_WRONLY, but this only
applies to system call side, meaning the BPF program has full
read/write access to the map as usual while bpf(2) calls with
map fd can either only read or write into the map depending
on the flags. BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG allows
for the exact opposite such that verifier is going to reject
program loads if write into a read-only map or a read into a
write-only map is detected. For read-only map case also some
helpers are forbidden for programs that would alter the map
state such as map deletion, update, etc. As opposed to the two
BPF_F_RDONLY / BPF_F_WRONLY flags, BPF_F_RDONLY_PROG as well
as BPF_F_WRONLY_PROG really do correspond to the map lifetime.
We've enabled this generic map extension to various non-special
maps holding normal user data: array, hash, lru, lpm, local
storage, queue and stack. Further generic map types could be
followed up in future depending on use-case. Main use case
here is to forbid writes into .rodata map values from verifier
side.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This generic extension to BPF maps allows for directly loading
an address residing inside a BPF map value as a single BPF
ldimm64 instruction!
The idea is similar to what BPF_PSEUDO_MAP_FD does today, which
is a special src_reg flag for ldimm64 instruction that indicates
that inside the first part of the double insns's imm field is a
file descriptor which the verifier then replaces as a full 64bit
address of the map into both imm parts. For the newly added
BPF_PSEUDO_MAP_VALUE src_reg flag, the idea is the following:
the first part of the double insns's imm field is again a file
descriptor corresponding to the map, and the second part of the
imm field is an offset into the value. The verifier will then
replace both imm parts with an address that points into the BPF
map value at the given value offset for maps that support this
operation. Currently supported is array map with single entry.
It is possible to support more than just single map element by
reusing both 16bit off fields of the insns as a map index, so
full array map lookup could be expressed that way. It hasn't
been implemented here due to lack of concrete use case, but
could easily be done so in future in a compatible way, since
both off fields right now have to be 0 and would correctly
denote a map index 0.
The BPF_PSEUDO_MAP_VALUE is a distinct flag as otherwise with
BPF_PSEUDO_MAP_FD we could not differ offset 0 between load of
map pointer versus load of map's value at offset 0, and changing
BPF_PSEUDO_MAP_FD's encoding into off by one to differ between
regular map pointer and map value pointer would add unnecessary
complexity and increases barrier for debugability thus less
suitable. Using the second part of the imm field as an offset
into the value does /not/ come with limitations since maximum
possible value size is in u32 universe anyway.
This optimization allows for efficiently retrieving an address
to a map value memory area without having to issue a helper call
which needs to prepare registers according to calling convention,
etc, without needing the extra NULL test, and without having to
add the offset in an additional instruction to the value base
pointer. The verifier then treats the destination register as
PTR_TO_MAP_VALUE with constant reg->off from the user passed
offset from the second imm field, and guarantees that this is
within bounds of the map value. Any subsequent operations are
normally treated as typical map value handling without anything
extra needed from verification side.
The two map operations for direct value access have been added to
array map for now. In future other types could be supported as
well depending on the use case. The main use case for this commit
is to allow for BPF loader support for global variables that
reside in .data/.rodata/.bss sections such that we can directly
load the address of them with minimal additional infrastructure
required. Loader support has been added in subsequent commits for
libbpf library.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Minor comment merge conflict in mlx5.
Staging driver has a fixup due to the skb->xmit_more changes
in 'net-next', but was removed in 'net'.
Signed-off-by: David S. Miller <davem@davemloft.net>
check_stack_access() that prints verbose log is used in
adjust_ptr_min_max_vals() that prints its own verbose log and now they
stick together, e.g.:
variable stack access var_off=(0xfffffffffffffff0; 0x4) off=-16
size=1R2 stack pointer arithmetic goes out of range, prohibited for
!root
Add missing newline so that log is more readable:
variable stack access var_off=(0xfffffffffffffff0; 0x4) off=-16 size=1
R2 stack pointer arithmetic goes out of range, prohibited for !root
Fixes: f1174f77b5 ("bpf/verifier: rework value tracking")
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
As discussed in [1] max value of variable offset has to be checked for
overflow on stack access otherwise verifier would accept code like this:
0: (b7) r2 = 6
1: (b7) r3 = 28
2: (7a) *(u64 *)(r10 -16) = 0
3: (7a) *(u64 *)(r10 -8) = 0
4: (79) r4 = *(u64 *)(r1 +168)
5: (c5) if r4 s< 0x0 goto pc+4
R1=ctx(id=0,off=0,imm=0) R2=inv6 R3=inv28
R4=inv(id=0,umax_value=9223372036854775807,var_off=(0x0;
0x7fffffffffffffff)) R10=fp0,call_-1 fp-8=mmmmmmmm fp-16=mmmmmmmm
6: (17) r4 -= 16
7: (0f) r4 += r10
8: (b7) r5 = 8
9: (85) call bpf_getsockopt#57
10: (b7) r0 = 0
11: (95) exit
, where R4 obviosly has unbounded max value.
Fix it by checking that reg->smax_value is inside (-BPF_MAX_VAR_OFF;
BPF_MAX_VAR_OFF) range.
reg->smax_value is used instead of reg->umax_value because stack
pointers are calculated using negative offset from fp. This is opposite
to e.g. map access where offset must be non-negative and where
umax_value is used.
Also dedicated verbose logs are added for both min and max bound check
failures to have diagnostics consistent with variable offset handling in
check_map_access().
[1] https://marc.info/?l=linux-netdev&m=155433357510597&w=2
Fixes: 2011fccfb6 ("bpf: Support variable offset stack access from helpers")
Reported-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Proper support of indirect stack access with variable offset in
unprivileged mode (!root) requires corresponding support in Spectre
masking for stack ALU in retrieve_ptr_limit().
There are no use-case for variable offset in unprivileged mode though so
make verifier reject such accesses for simplicity.
Pointer arithmetics is one (and only?) way to cause variable offset and
it's already rejected in unpriv mode so that verifier won't even get to
helper function whose argument contains variable offset, e.g.:
0: (7a) *(u64 *)(r10 -16) = 0
1: (7a) *(u64 *)(r10 -8) = 0
2: (61) r2 = *(u32 *)(r1 +0)
3: (57) r2 &= 4
4: (17) r2 -= 16
5: (0f) r2 += r10
variable stack access var_off=(0xfffffffffffffff0; 0x4) off=-16 size=1R2
stack pointer arithmetic goes out of range, prohibited for !root
Still it looks like a good idea to reject variable offset indirect stack
access for unprivileged mode in check_stack_boundary() explicitly.
Fixes: 2011fccfb6 ("bpf: Support variable offset stack access from helpers")
Reported-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
It's hard to guarantee that whole memory is marked as initialized on
helper return if uninitialized stack is accessed with variable offset
since specific bounds are unknown to verifier. This may cause
uninitialized stack leaking.
Reject such an access in check_stack_boundary to prevent possible
leaking.
There are no known use-cases for indirect uninitialized stack access
with variable offset so it shouldn't break anything.
Fixes: 2011fccfb6 ("bpf: Support variable offset stack access from helpers")
Reported-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
The existing 16Mbyte verifier log limit is not enough for log_level=2
even for small programs. Increase it to 1Gbyte.
Note it's not a kernel memory limit.
It's an amount of memory user space provides to store
the verifier log. The kernel populates it 1k at a time.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Large verifier speed improvements allow to increase
verifier complexity limit.
Now regardless of the program composition and its size it takes
little time for the verifier to hit insn_processed limit.
On typical x86 machine non-debug kernel processes 1M instructions
in 1/10 of a second.
(before these speed improvements specially crafted programs
could be hitting multi-second verification times)
Full kasan kernel with debug takes ~1 second for the same 1M insns.
Hence bump the BPF_COMPLEXITY_LIMIT_INSNS limit to 1M.
Also increase the number of instructions per program
from 4k to internal BPF_COMPLEXITY_LIMIT_INSNS limit.
4k limit was confusing to users, since small programs with hundreds
of insns could be hitting BPF_COMPLEXITY_LIMIT_INSNS limit.
Sometimes adding more insns and bpf_trace_printk debug statements
would make the verifier accept the program while removing
code would make the verifier reject it.
Some user space application started to add #define MAX_FOO to
their programs and do:
MAX_FOO=100;
again:
compile with MAX_FOO;
try to load;
if (fails_to_load) { reduce MAX_FOO; goto again; }
to be able to fit maximum amount of processing into single program.
Other users artificially split their single program into a set of programs
and use all 32 iterations of tail_calls to increase compute limits.
And the most advanced folks used unlimited tc-bpf filter list
to execute many bpf programs.
Essentially the users managed to workaround 4k insn limit.
This patch removes the limit for root programs from uapi.
BPF_COMPLEXITY_LIMIT_INSNS is the kernel internal limit
and success to load the program no longer depends on program size,
but on 'smartness' of the verifier only.
The verifier will continue to get smarter with every kernel release.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Larger programs may trigger 16-bit jump offset overflow check
during instruction patching. Make this error verbose otherwise
users cannot decipher error code without printks in the verifier.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Temporary arrays used during program verification need to be vmalloc-ed
to support large bpf programs.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
With large verifier speed improvement brought by the previous patch
mark_reg_read() becomes the hottest function during verification.
On a typical program it consumes 40% of cpu.
mark_reg_read() walks parentage chain of registers to mark parents as LIVE_READ.
Once the register is marked there is no need to remark it again in the future.
Hence stop walking the chain once first LIVE_READ is seen.
This optimization drops mark_reg_read() time from 40% of cpu to <1%
and overall 2x improvement of verification speed.
For some programs the longest_mark_read_walk counter improves from ~500 to ~5
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
