linux/kernel
Jakub Kicinski 7640ead939 bpf: verifier: make sure callees don't prune with caller differences
Currently for liveness and state pruning the register parentage
chains don't include states of the callee.  This makes some sense
as the callee can't access those registers.  However, this means
that READs done after the callee returns will not propagate into
the states of the callee.  Callee will then perform pruning
disregarding differences in caller state.

Example:

   0: (85) call bpf_user_rnd_u32
   1: (b7) r8 = 0
   2: (55) if r0 != 0x0 goto pc+1
   3: (b7) r8 = 1
   4: (bf) r1 = r8
   5: (85) call pc+4
   6: (15) if r8 == 0x1 goto pc+1
   7: (05) *(u64 *)(r9 - 8) = r3
   8: (b7) r0 = 0
   9: (95) exit

   10: (15) if r1 == 0x0 goto pc+0
   11: (95) exit

Here we acquire unknown state with call to get_random() [1].  Then
we store this random state in r8 (either 0 or 1) [1 - 3], and make
a call on line 5.  Callee does nothing but a trivial conditional
jump (to create a pruning point).  Upon return caller checks the
state of r8 and either performs an unsafe read or not.

Verifier will first explore the path with r8 == 1, creating a pruning
point at [11].  The parentage chain for r8 will include only callers
states so once verifier reaches [6] it will mark liveness only on states
in the caller, and not [11].  Now when verifier walks the paths with
r8 == 0 it will reach [11] and since REG_LIVE_READ on r8 was not
propagated there it will prune the walk entirely (stop walking
the entire program, not just the callee).  Since [6] was never walked
with r8 == 0, [7] will be considered dead and replaced with "goto -1"
causing hang at runtime.

This patch weaves the callee's explored states onto the callers
parentage chain.  Rough parentage for r8 would have looked like this
before:

[0] [1] [2] [3] [4] [5]   [10]      [11]      [6]      [7]
     |           |      ,---|----.    |        |        |
  sl0:         sl0:    / sl0:     \ sl0:      sl0:     sl0:
  fr0: r8 <-- fr0: r8<+--fr0: r8   `fr0: r8  ,fr0: r8<-fr0: r8
                       \ fr1: r8 <- fr1: r8 /
                        \__________________/

after:

[0] [1] [2] [3] [4] [5]   [10]      [11]      [6]      [7]
     |           |          |         |        |        |
   sl0:         sl0:      sl0:       sl0:      sl0:     sl0:
   fr0: r8 <-- fr0: r8 <- fr0: r8 <- fr0: r8 <-fr0: r8<-fr0: r8
                          fr1: r8 <- fr1: r8

Now the mark from instruction 6 will travel through callees states.

Note that we don't have to connect r0 because its overwritten by
callees state on return and r1 - r5 because those are not alive
any more once a call is made.

v2:
 - don't connect the callees registers twice (Alexei: suggestion & code)
 - add more details to the comment (Ed & Alexei)
v1: don't unnecessarily link caller saved regs (Jiong)

Fixes: f4d7e40a5b ("bpf: introduce function calls (verification)")
Reported-by: David Beckett <david.beckett@netronome.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-12-13 10:35:40 -08:00
..
bpf bpf: verifier: make sure callees don't prune with caller differences 2018-12-13 10:35:40 -08:00
cgroup for-linus-20181102 2018-11-02 11:25:48 -07:00
configs kvm_config: add CONFIG_VIRTIO_MENU 2018-10-24 20:55:56 -04:00
debug kdb: kdb_support: mark expected switch fall-throughs 2018-11-13 20:38:50 +00:00
dma swiotlb: Skip cache maintenance on map error 2018-11-21 18:47:58 +01:00
events Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-11-03 18:13:43 -07:00
gcov gcov: remove CONFIG_GCOV_FORMAT_AUTODETECT 2018-06-08 18:56:02 +09:00
irq irq/matrix: Fix memory overallocation 2018-11-01 10:00:38 +01:00
livepatch Merge branch 'for-4.19/upstream' into for-linus 2018-08-20 18:33:50 +02:00
locking mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
power memblock: stop using implicit alignment to SMP_CACHE_BYTES 2018-10-31 08:54:16 -07:00
printk mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
rcu Merge branches 'doc.2018.08.30a', 'dynticks.2018.08.30b', 'srcu.2018.08.30b' and 'torture.2018.08.29a' into HEAD 2018-08-30 16:12:53 -07:00
sched Merge branch 'akpm' (patches from Andrew) 2018-11-18 11:31:26 -08:00
time posix-cpu-timers: Remove useless call to check_dl_overrun() 2018-11-08 07:43:35 +01:00
trace bpf: fix check of allowed specifiers in bpf_trace_printk 2018-11-23 21:54:14 +01:00
.gitignore
acct.c
async.c kernel/async.c: revert "async: simplify lowest_in_progress()" 2018-02-06 18:32:44 -08:00
audit_fsnotify.c fsnotify: add fsnotify_add_inode_mark() wrappers 2018-05-18 14:58:22 +02:00
audit_tree.c \n 2018-08-17 09:41:28 -07:00
audit_watch.c audit: fix use-after-free in audit_add_watch 2018-07-18 11:43:36 -04:00
audit.c audit: use ktime_get_coarse_real_ts64() for timestamps 2018-07-17 14:45:08 -04:00
audit.h audit: track the owner of the command mutex ourselves 2018-02-23 11:22:22 -05:00
auditfilter.c audit: rename FILTER_TYPE to FILTER_EXCLUDE 2018-06-19 10:39:54 -04:00
auditsc.c audit/stable-4.18 PR 20180814 2018-08-15 10:46:54 -07:00
backtracetest.c
bounds.c kbuild: fix kernel/bounds.c 'W=1' warning 2018-10-31 08:54:14 -07:00
capability.c
compat.c y2038: globally rename compat_time to old_time32 2018-08-27 14:48:48 +02:00
configs.c
context_tracking.c
cpu_pm.c
cpu.c Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-10-23 18:43:04 +01:00
crash_core.c kernel/crash_core.c: print timestamp using time64_t 2018-08-22 10:52:47 -07:00
crash_dump.c
cred.c
delayacct.c delayacct: track delays from thrashing cache pages 2018-10-26 16:26:32 -07:00
dma.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
elfcore.c
exec_domain.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
exit.c signal: Pass pid type into group_send_sig_info 2018-07-21 12:57:35 -05:00
extable.c extable: Make init_kernel_text() global 2018-02-21 16:54:06 +01:00
fail_function.c kernel/fail_function.c: remove meaningless null pointer check before debugfs_remove_recursive 2018-10-31 08:54:12 -07:00
fork.c New gcc plugin: stackleak 2018-11-01 11:46:27 -07:00
freezer.c PM / reboot: Eliminate race between reboot and suspend 2018-08-06 12:35:20 +02:00
futex_compat.c y2038: globally rename compat_time to old_time32 2018-08-27 14:48:48 +02:00
futex.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
groups.c
hung_task.c kernel: hung_task.c: disable on suspend 2018-10-25 18:45:08 +02:00
iomem.c memremap: split devm_memremap_pages() and memremap() infrastructure 2018-05-15 23:08:33 -07:00
irq_work.c
jump_label.c Merge branch 'x86/build' into locking/core, to pick up dependent patches and unify jump-label work 2018-10-16 17:30:11 +02:00
kallsyms.c kallsyms: reduce size a little on 64-bit 2018-09-10 22:54:33 +09:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt kconfig: include kernel/Kconfig.preempt from init/Kconfig 2018-08-02 08:06:54 +09:00
kcov.c sched/core / kcov: avoid kcov_area during task switch 2018-06-15 07:55:24 +09:00
kexec_core.c kexec: Allocate decrypted control pages for kdump if SME is enabled 2018-10-06 12:01:51 +02:00
kexec_file.c kernel/kexec_file.c: remove some duplicated includes 2018-11-03 10:09:37 -07:00
kexec_internal.h
kexec.c kexec: add call to LSM hook in original kexec_load syscall 2018-07-16 12:31:57 -07:00
kmod.c
kprobes.c kprobes: Don't call BUG_ON() if there is a kprobe in use on free list 2018-09-12 08:01:16 +02:00
ksysfs.c
kthread.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-08-13 11:25:07 -07:00
latencytop.c
Makefile x86/entry: Add STACKLEAK erasing the kernel stack at the end of syscalls 2018-09-04 10:35:47 -07:00
memremap.c Merge branch 'xarray' of git://git.infradead.org/users/willy/linux-dax 2018-10-28 11:35:40 -07:00
module_signing.c modsign: log module name in the event of an error 2018-07-02 11:36:17 +02:00
module-internal.h modsign: log module name in the event of an error 2018-07-02 11:36:17 +02:00
module.c jump_table: Move entries into ro_after_init region 2018-09-27 17:56:49 +02:00
notifier.c
nsproxy.c
padata.c
panic.c kernel/panic.c: filter out a potential trailing newline 2018-10-31 08:54:14 -07:00
params.c kernel/params.c: downgrade warning for unsafe parameters 2018-04-11 10:28:37 -07:00
pid_namespace.c signal: Use group_send_sig_info to kill all processes in a pid namespace 2018-09-16 16:08:25 +02:00
pid.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
profile.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
ptrace.c Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2018-10-24 11:22:39 +01:00
range.c
reboot.c kernel/reboot.c: export pm_power_off_prepare 2018-09-11 16:13:24 +01:00
relay.c kernel/relay.c: change return type to vm_fault_t 2018-06-15 07:55:24 +09:00
resource.c resource/docs: Complete kernel-doc style function documentation 2018-11-07 16:47:47 +01:00
rseq.c rseq: uapi: Declare rseq_cs field as union, update includes 2018-07-10 22:18:52 +02:00
seccomp.c Merge branch 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2018-10-24 11:49:35 +01:00
signal.c kernel/signal.c: fix a comment error 2018-10-31 08:54:14 -07:00
smp.c smp,cpumask: introduce on_each_cpu_cond_mask 2018-10-09 16:51:11 +02:00
smpboot.c smpboot: Remove cpumask from the API 2018-07-03 09:20:44 +02:00
smpboot.h
softirq.c Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-10-25 11:43:47 -07:00
stackleak.c stackleak: Allow runtime disabling of kernel stack erasing 2018-09-04 10:35:48 -07:00
stacktrace.c
stop_machine.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-08-13 11:25:07 -07:00
sys_ni.c Merge branch 'core-rseq-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-06-10 10:17:09 -07:00
sys.c kernel/sys.c: remove duplicated include 2018-09-20 22:01:11 +02:00
sysctl_binary.c staging: irda: remove remaining remants of irda code removal 2018-04-16 11:26:49 +02:00
sysctl.c kernel/sysctl.c: remove duplicated include 2018-11-03 10:09:37 -07:00
task_work.c
taskstats.c pids: introduce find_get_task_by_vpid() helper 2018-02-06 18:32:46 -08:00
test_kprobes.c kprobes: Remove jprobe API implementation 2018-06-21 12:33:05 +02:00
torture.c rcutorture: Check GP completion at stutter end 2018-08-29 09:20:48 -07:00
tracepoint.c tracepoint: Fix tracepoint array element size mismatch 2018-10-17 15:35:29 -04:00
tsacct.c
ucount.c headers: untangle kmemleak.h from mm.h 2018-04-05 21:36:27 -07:00
uid16.c fs: add do_fchownat(), ksys_fchown() helpers and ksys_{,l}chown() wrappers 2018-04-02 20:15:59 +02:00
uid16.h kernel: provide ksys_*() wrappers for syscalls called by kernel/uid16.c 2018-04-02 20:15:30 +02:00
umh.c umh: Add command line to user mode helpers 2018-10-22 19:37:36 -07:00
up.c smp,cpumask: introduce on_each_cpu_cond_mask 2018-10-09 16:51:11 +02:00
user_namespace.c userns: also map extents in the reverse map to kernel IDs 2018-11-07 23:51:16 -06:00
user-return-notifier.c
user.c userns: use irqsave variant of refcount_dec_and_lock() 2018-08-22 10:52:47 -07:00
utsname_sysctl.c sys: don't hold uts_sem while accessing userspace memory 2018-08-11 02:05:53 -05:00
utsname.c uts: create "struct uts_namespace" from kmem_cache 2018-04-11 10:28:35 -07:00
watchdog_hld.c watchdog: Mark watchdog touch functions as notrace 2018-08-30 12:56:40 +02:00
watchdog.c watchdog: Mark watchdog touch functions as notrace 2018-08-30 12:56:40 +02:00
workqueue_internal.h workqueue: Set worker->desc to workqueue name by default 2018-05-18 08:47:13 -07:00
workqueue.c watchdog: Mark watchdog touch functions as notrace 2018-08-30 12:56:40 +02:00