linux/kernel/bpf
Toke Høiland-Jørgensen 54713c85f5 bpf: Fix potential race in tail call compatibility check
Lorenzo noticed that the code testing for program type compatibility of
tail call maps is potentially racy in that two threads could encounter a
map with an unset type simultaneously and both return true even though they
are inserting incompatible programs.

The race window is quite small, but artificially enlarging it by adding a
usleep_range() inside the check in bpf_prog_array_compatible() makes it
trivial to trigger from userspace with a program that does, essentially:

        map_fd = bpf_create_map(BPF_MAP_TYPE_PROG_ARRAY, 4, 4, 2, 0);
        pid = fork();
        if (pid) {
                key = 0;
                value = xdp_fd;
        } else {
                key = 1;
                value = tc_fd;
        }
        err = bpf_map_update_elem(map_fd, &key, &value, 0);

While the race window is small, it has potentially serious ramifications in
that triggering it would allow a BPF program to tail call to a program of a
different type. So let's get rid of it by protecting the update with a
spinlock. The commit in the Fixes tag is the last commit that touches the
code in question.

v2:
- Use a spinlock instead of an atomic variable and cmpxchg() (Alexei)
v3:
- Put lock and the members it protects into an embedded 'owner' struct (Daniel)

Fixes: 3324b584b6 ("ebpf: misc core cleanup")
Reported-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211026110019.363464-1-toke@redhat.com
2021-10-26 12:37:28 -07:00
..
preload libbpf: Move BPF_SEQ_PRINTF and BPF_SNPRINTF to bpf_helpers.h 2021-05-26 10:45:41 -07:00
arraymap.c bpf: Fix potential race in tail call compatibility check 2021-10-26 12:37:28 -07:00
bpf_inode_storage.c bpf: Fix spelling mistakes 2021-05-24 21:13:05 -07:00
bpf_iter.c bpf: Refactor BPF_PROG_RUN into a function 2021-08-17 00:45:07 +02:00
bpf_local_storage.c bpf: Prevent deadlock from recursive bpf_task_storage_[get|delete] 2021-02-26 11:51:48 -08:00
bpf_lru_list.c bpf_lru_list: Read double-checked variable once without lock 2021-02-10 15:54:26 -08:00
bpf_lru_list.h bpf: Fix a typo "inacitve" -> "inactive" 2020-04-06 21:54:10 +02:00
bpf_lsm.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2021-06-17 11:54:56 -07:00
bpf_struct_ops_types.h bpf: tcp: Support tcp_congestion_ops in bpf 2020-01-09 08:46:18 -08:00
bpf_struct_ops.c bpf: Handle return value of BPF_PROG_TYPE_STRUCT_OPS prog 2021-09-14 11:09:50 -07:00
bpf_task_storage.c bpf: Consolidate task_struct BTF_ID declarations 2021-08-25 10:37:05 -07:00
btf.c bpf: Fix bpf-next builds without CONFIG_BPF_EVENTS 2021-08-25 19:41:39 -07:00
cgroup.c bpf: Migrate cgroup_bpf to internal cgroup_bpf_attach_type enum 2021-08-23 17:50:24 -07:00
core.c bpf: Fix potential race in tail call compatibility check 2021-10-26 12:37:28 -07:00
cpumap.c bpf: cpumap: Implement generic cpumap 2021-07-07 20:01:45 -07:00
devmap.c bpf, devmap: Exclude XDP broadcast to master device 2021-08-09 23:25:14 +02:00
disasm.c bpf: Relicense disassembler as GPL-2.0-only OR BSD-2-Clause 2021-09-02 14:49:23 +02:00
disasm.h bpf: Relicense disassembler as GPL-2.0-only OR BSD-2-Clause 2021-09-02 14:49:23 +02:00
dispatcher.c bpf: Remove bpf_image tree 2020-03-13 12:49:52 -07:00
hashtab.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2021-08-13 06:41:22 -07:00
helpers.c Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2021-08-30 16:42:47 -07:00
inode.c bpf: Fix regression on BPF_OBJ_GET with non-O_RDWR flags 2021-06-22 14:57:43 +02:00
Kconfig sock_map: Relax config dependency to CONFIG_NET 2021-07-15 18:17:49 -07:00
local_storage.c bpf: Increase supported cgroup storage value size 2021-07-27 15:59:29 -07:00
lpm_trie.c bpf: Allow RCU-protected lookups to happen from bh context 2021-06-24 19:41:15 +02:00
Makefile bpf: Enable task local storage for tracing programs 2021-02-26 11:51:47 -08:00
map_in_map.c bpf: Remember BTF of inner maps. 2021-07-15 22:31:10 +02:00
map_in_map.h bpf: Add map_meta_equal map ops 2020-08-28 15:41:30 +02:00
map_iter.c bpf: Implement link_query callbacks in map element iterators 2020-08-21 14:01:39 -07:00
net_namespace.c bpf: Add support for forced LINK_DETACH command 2020-08-01 20:38:28 -07:00
offload.c bpf, offload: Replace bitwise AND by logical AND in bpf_prog_offload_info_fill 2020-02-17 16:53:49 +01:00
percpu_freelist.c bpf: Use raw_spin_trylock() for pcpu_freelist_push/pop in NMI 2020-10-06 00:04:11 +02:00
percpu_freelist.h bpf: Use raw_spin_trylock() for pcpu_freelist_push/pop in NMI 2020-10-06 00:04:11 +02:00
prog_iter.c bpf: Refactor bpf_iter_reg to have separate seq_info member 2020-07-25 20:16:32 -07:00
queue_stack_maps.c bpf: Eliminate rlimit-based memory accounting for queue_stack_maps maps 2020-12-02 18:32:46 -08:00
reuseport_array.c bpf: Fix spelling mistakes 2021-05-24 21:13:05 -07:00
ringbuf.c bpf: Fix false positive kmemleak report in bpf_ringbuf_area_alloc() 2021-06-28 15:57:46 +02:00
stackmap.c bpf: Fix integer overflow in prealloc_elems_and_freelist() 2021-09-30 16:17:23 +02:00
syscall.c bpf: Fix potential race in tail call compatibility check 2021-10-26 12:37:28 -07:00
sysfs_btf.c bpf: Load and verify kernel module BTFs 2020-11-10 15:25:53 -08:00
task_iter.c bpf: Consolidate task_struct BTF_ID declarations 2021-08-25 10:37:05 -07:00
tnum.c bpf, tnums: Provably sound, faster, and more precise algorithm for tnum_mul 2021-06-01 13:34:15 +02:00
trampoline.c bpf: Refactor BPF_PROG_RUN into a function 2021-08-17 00:45:07 +02:00
verifier.c bpf: Add oversize check before call kvcalloc() 2021-09-13 16:28:15 -07:00