From: sashiko-bot@kernel.org
To: "Eduard Zingerman" <eddyz87@gmail.com>
Cc: bpf@vger.kernel.org
Subject: Re: [PATCH bpf 03/10] bpf: mark a NULL memory argument of a call precise
Date: Sat, 05 Sep 2026 00:23:57 +0000 [thread overview]
Message-ID: <20260905002358.04E2E1F00A3D@smtp.kernel.org> (raw)
In-Reply-To: <20260904-register-is-null-precise-fixes-v1-3-0f5a360ff15d@gmail.com>
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Uninitialized variable `known_memory` is read on the error path in `check_kfunc_args` when handling NULL memory arguments.
--
commit 00db4f1dea6ce217e9633f69c742a410441956c2
Author: Eduard Zingerman <eddyz87@gmail.com>
bpf: mark a NULL memory argument of a call precise
This commit ensures that a NULL memory argument is correctly marked precise
to prevent pruning against arbitrary scalar values. It also introduces a new
mark_arg_precision() helper to handle arguments that reside on the stack.
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index ca362a7ea58c3..b758f28227540 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
[ ... ]
> @@ -7168,7 +7177,7 @@ 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);
[Severity: Medium]
Does this early return path leave the `known_memory` pointer uninitialized
if `mark_arg_precision()` fails?
Looking at its caller in `check_kfunc_args()`, `known_memory` is declared
without initialization:
kernel/bpf/verifier.c:check_kfunc_args() {
...
bool known_memory;
...
ret = check_mem_reg(env, reg, argno, type_size, BPF_READ | BPF_WRITE,
meta, &known_memory);
if (ret < 0) {
...
if (known_memory)
verbose(env, "...");
else
verbose(env, "...");
return ret;
}
...
}
If `mark_arg_precision()` returns a negative error code (like `-EFAULT` from
backtracking depth limits), `check_mem_reg()` will propagate it immediately
before reaching the `if (known_memory) *known_memory = true;` block.
Could this cause `check_kfunc_args()` to evaluate an uninitialized boolean
variable when deciding which diagnostic message to print on the error path?
> if (known_memory)
> *known_memory = true;
>
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260904-register-is-null-precise-fixes-v1-0-0f5a360ff15d@gmail.com?part=3
next prev parent reply other threads:[~2026-09-05 0:23 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-05 0:05 [PATCH bpf 00/10] bpf: add missing precision propagation after bpf_register_is_null calls Eduard Zingerman
2026-09-05 0:05 ` [PATCH bpf 01/10] bpf: mark a NULL call argument precise Eduard Zingerman
2026-09-05 0:21 ` sashiko-bot
2026-09-05 0:05 ` [PATCH bpf 02/10] selftests/bpf: precision of a NULL helper argument Eduard Zingerman
2026-09-05 0:05 ` [PATCH bpf 03/10] bpf: mark a NULL memory argument of a call precise Eduard Zingerman
2026-09-05 0:23 ` sashiko-bot [this message]
2026-09-05 0:51 ` bot+bpf-ci
2026-09-05 0:05 ` [PATCH bpf 04/10] selftests/bpf: precision of a NULL global subprogram memory argument Eduard Zingerman
2026-09-05 0:51 ` bot+bpf-ci
2026-09-05 0:05 ` [PATCH bpf 05/10] bpf: mark a NULL kfunc argument precise Eduard Zingerman
2026-09-05 0:51 ` bot+bpf-ci
2026-09-05 0:05 ` [PATCH bpf 06/10] selftests/bpf: precision of a NULL kfunc argument Eduard Zingerman
2026-09-05 0:05 ` [PATCH bpf 07/10] bpf: mark a NULL BTF_ID argument of a global subprogram precise Eduard Zingerman
2026-09-05 0:19 ` sashiko-bot
2026-09-05 0:05 ` [PATCH bpf 08/10] selftests/bpf: precision of a NULL global subprogram BTF_ID argument Eduard Zingerman
2026-09-05 0:06 ` [PATCH bpf 09/10] bpf: propagate mark_chain_precision() errors out of loop_flag_is_zero() Eduard Zingerman
2026-09-05 0:06 ` [PATCH bpf 10/10] bpf: use mark_arg_precision() in check_mem_size_reg() Eduard Zingerman
2026-09-05 0:51 ` bot+bpf-ci
2026-09-05 1:20 ` [PATCH bpf 00/10] bpf: add missing precision propagation after bpf_register_is_null calls patchwork-bot+netdevbpf
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