diff options
| author | Andrii Nakryiko <andrii@kernel.org> | 2023-09-18 14:01:10 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2023-09-20 03:26:25 -0700 |
| commit | 81335f90e8a88b81932df011105c46e708744f44 (patch) | |
| tree | 0a13b2a8d05d69f718ca73660e6431db866d2f0e /kernel | |
| parent | b724a6418f1f853bcb39c8923bf14a50c7bdbd07 (diff) | |
bpf: unconditionally reset backtrack_state masks on global func exit
In mark_chain_precision() logic, when we reach the entry to a global
func, it is expected that R1-R5 might be still requested to be marked
precise. This would correspond to some integer input arguments being
tracked as precise. This is all expected and handled as a special case.
What's not expected is that we'll leave backtrack_state structure with
some register bits set. This is because for subsequent precision
propagations backtrack_state is reused without clearing masks, as all
code paths are carefully written in a way to leave empty backtrack_state
with zeroed out masks, for speed.
The fix is trivial, we always clear register bit in the register mask, and
then, optionally, set reg->precise if register is SCALAR_VALUE type.
Reported-by: Chris Mason <clm@meta.com>
Fixes: be2ef8161572 ("bpf: allow precision tracking for programs with subprogs")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230918210110.2241458-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/verifier.c | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index bb78212fa5b2..c0c7d137066a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4047,11 +4047,9 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno) bitmap_from_u64(mask, bt_reg_mask(bt)); for_each_set_bit(i, mask, 32) { reg = &st->frame[0]->regs[i]; - if (reg->type != SCALAR_VALUE) { - bt_clear_reg(bt, i); - continue; - } - reg->precise = true; + bt_clear_reg(bt, i); + if (reg->type == SCALAR_VALUE) + reg->precise = true; } return 0; } |