diff options
| author | Yonghong Song <yhs@fb.com> | 2019-12-04 17:06:06 -0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2019-12-04 21:20:07 -0800 |
| commit | e9eeec58c992c47b394e4f829e4f81b923b0a322 (patch) | |
| tree | a77691b0ca01393ba337e39261c0d3c2e5225ac8 /kernel/bpf/verifier.c | |
| parent | ef8c84effce3c7a0b8196fcda8f430c815ab511c (diff) | |
bpf: Fix a bug when getting subprog 0 jited image in check_attach_btf_id
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: 5b92a28aae4d ("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
Diffstat (limited to 'kernel/bpf/verifier.c')
| -rw-r--r-- | kernel/bpf/verifier.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a0482e1c4a77..034ef81f935b 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -9636,7 +9636,10 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) ret = -EINVAL; goto out; } - addr = (long) tgt_prog->aux->func[subprog]->bpf_func; + if (subprog == 0) + addr = (long) tgt_prog->bpf_func; + else + addr = (long) tgt_prog->aux->func[subprog]->bpf_func; } else { addr = kallsyms_lookup_name(tname); if (!addr) { |