From: Eduard Zingerman <eddyz87@gmail.com>
To: Luis Gerhorst <luis.gerhorst@fau.de>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
John Fastabend <john.fastabend@gmail.com>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>,
Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Henriette Herzog <henriette.herzog@rub.de>,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: syzbot+b5eb72a560b8149a1885@syzkaller.appspotmail.com
Subject: Re: [PATCH bpf-next] bpf: Fix state use-after-free on push_stack() err
Date: Wed, 11 Jun 2025 15:23:06 -0700 [thread overview]
Message-ID: <01c816691c132dd6c8c2588f396b240f033ce201.camel@gmail.com> (raw)
In-Reply-To: <20250611210728.266563-1-luis.gerhorst@fau.de>
On Wed, 2025-06-11 at 23:07 +0200, Luis Gerhorst wrote:
[...]
> Signed-off-by: Luis Gerhorst <luis.gerhorst@fau.de>
I reproduced the error locally and this patch fixes it.
Also double-checked places where free_verifier_state is called
and error codes used in error_recoverable_with_nospec() are used.
Looks like env->cur_state should be always ok if
error_recoverable_with_nospec() recovers, env internal structures
in healthy state.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
> ---
> kernel/bpf/verifier.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index b1f797616f20..d3bff0385a55 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -14229,7 +14229,7 @@ static int sanitize_err(struct bpf_verifier_env *env,
> case REASON_STACK:
> verbose(env, "R%d could not be pushed for speculative verification, %s\n",
> dst, err);
> - break;
> + return -ENOMEM;
Good catch, I would have probably missed it.
> default:
> verbose(env, "verifier internal error: unknown reason (%d)\n",
> reason);
> @@ -19753,7 +19753,7 @@ static int do_check(struct bpf_verifier_env *env)
> goto process_bpf_exit;
>
> err = do_check_insn(env, &do_print_state);
> - if (state->speculative && error_recoverable_with_nospec(err)) {
> + if (error_recoverable_with_nospec(err) && state->speculative) {
> /* Prevent this speculative path from ever reaching the
> * insn that would have been unsafe to execute.
> */
>
> base-commit: 2d72dd14d77f31a7caa619fe0b889304844e612e
next prev parent reply other threads:[~2025-06-11 22:23 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-11 12:36 [syzbot] [bpf?] KASAN: slab-use-after-free Read in do_check syzbot
2025-06-11 13:02 ` Eduard Zingerman
2025-06-11 14:03 ` Luis Gerhorst
2025-06-11 17:20 ` Eduard Zingerman
2025-06-11 21:07 ` [PATCH bpf-next] bpf: Fix state use-after-free on push_stack() err Luis Gerhorst
2025-06-11 22:23 ` Eduard Zingerman [this message]
2025-06-11 23:10 ` patchwork-bot+netdevbpf
2025-06-11 21:14 ` [PATCH bpf-next] bpf: Remove redundant free_verifier_state()/pop_stack() Luis Gerhorst
2025-06-11 22:36 ` Eduard Zingerman
2025-06-13 9:01 ` [PATCH bpf-next v2] " Luis Gerhorst
2025-06-13 21:17 ` Eduard Zingerman
2025-06-13 22:06 ` Alexei Starovoitov
2025-06-13 9:07 ` [PATCH bpf-next] " Luis Gerhorst
2025-06-11 21:32 ` [syzbot] [bpf?] KASAN: slab-use-after-free Read in do_check Luis Gerhorst
2025-06-11 21:43 ` Eduard Zingerman
2025-06-11 21:40 ` Eduard Zingerman
2025-06-11 23:00 ` syzbot
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