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| author | Eduard Zingerman <eddyz87@gmail.com> | 2026-09-04 17:05:54 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2026-09-04 18:17:30 -0700 |
| commit | f1e418129f2ebb5376df2f1cd19720fa80f8adb4 (patch) | |
| tree | 1014f7b6324d46f07d016501547346a3727c78ed | |
| parent | 593c8eb0fb91a24c39244a7f9e7d04412d750544 (diff) | |
| download | linux-f1e418129f2ebb5376df2f1cd19720fa80f8adb4.tar.gz linux-f1e418129f2ebb5376df2f1cd19720fa80f8adb4.zip | |
bpf: mark a NULL memory argument of a call precise
check_mem_reg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.
The argument may live on the stack rather than in a register when a
call has more than MAX_BPF_FUNC_REG_ARGS arguments, hence the new
mark_arg_precision() helper.
Fixes: e5069b9c23b3 ("bpf: Support pointers in global func args")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-3-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
| -rw-r--r-- | kernel/bpf/verifier.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b107f551a62d..7926e131b1cb 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4246,6 +4246,15 @@ static int mark_stack_arg_precision(struct bpf_verifier_env *env, int arg_idx) return mark_chain_precision_batch(env, env->cur_state); } +static int mark_arg_precision(struct bpf_verifier_env *env, argno_t argno) +{ + int regno = reg_from_argno(argno); + + if (regno >= 0) + return mark_chain_precision(env, regno); + return mark_stack_arg_precision(env, arg_idx_from_argno(argno)); +} + static int check_outgoing_stack_args(struct bpf_verifier_env *env, struct bpf_func_state *caller, int nargs, const char *callee_name, const struct btf *btf, const struct btf_param *args) @@ -7175,7 +7184,7 @@ static int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg int size, err = 0; if (bpf_register_is_null(reg)) - return 0; + return mark_arg_precision(env, argno); if (known_memory) *known_memory = true; |