bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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

  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=01c816691c132dd6c8c2588f396b240f033ce201.camel@gmail.com \
    --to=eddyz87@gmail.com \
    --cc=andrii@kernel.org \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=haoluo@google.com \
    --cc=henriette.herzog@rub.de \
    --cc=john.fastabend@gmail.com \
    --cc=jolsa@kernel.org \
    --cc=kpsingh@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luis.gerhorst@fau.de \
    --cc=martin.lau@linux.dev \
    --cc=memxor@gmail.com \
    --cc=sdf@fomichev.me \
    --cc=song@kernel.org \
    --cc=syzbot+b5eb72a560b8149a1885@syzkaller.appspotmail.com \
    --cc=yonghong.song@linux.dev \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).