From: Paul Chaignon <paul.chaignon@gmail.com>
To: syzbot <syzbot+ccac90e482b2a81d74aa@syzkaller.appspotmail.com>
Cc: andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
daniel@iogearbox.net, eddyz87@gmail.com, haoluo@google.com,
john.fastabend@gmail.com, jolsa@kernel.org, kpsingh@kernel.org,
linux-kernel@vger.kernel.org, martin.lau@linux.dev,
sdf@fomichev.me, song@kernel.org,
syzkaller-bugs@googlegroups.com, yonghong.song@linux.dev
Subject: Re: [syzbot] [bpf?] WARNING in convert_ctx_accesses
Date: Thu, 31 Jul 2025 15:53:43 +0200 [thread overview]
Message-ID: <aIt1MuiclSoonZLe@mail.gmail.com> (raw)
In-Reply-To: <688b72e9.050a0220.5d226.0018.GAE@google.com>
This is happening because flow_dissector_is_valid_access matches on
ranges (bpf_ctx_range) whereas flow_dissector_convert_ctx_access matches
on offsets (offsetof). Hence an access to
offsetof(struct __sk_buff, data_end) + 1 is considered valid and then
fails during convertion.
I'll send a fix asap.
Paul
On Thu, Jul 31, 2025 at 06:43:05AM -0700, syzbot wrote:
> syzbot has bisected this issue to:
>
> commit 0df1a55afa832f463f9ad68ddc5de92230f1bc8a
> Author: Paul Chaignon <paul.chaignon@gmail.com>
> Date: Tue Jul 1 18:36:15 2025 +0000
>
> bpf: Warn on internal verifier errors
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17d6aca2580000
> start commit: e8d780dcd957 Merge tag 'slab-for-6.17' of git://git.kernel..
> git tree: upstream
> final oops: https://syzkaller.appspot.com/x/report.txt?x=1436aca2580000
> console output: https://syzkaller.appspot.com/x/log.txt?x=1036aca2580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=d32de89be62206c8
> dashboard link: https://syzkaller.appspot.com/bug?extid=ccac90e482b2a81d74aa
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=131049bc580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11cc2cf0580000
>
> Reported-by: syzbot+ccac90e482b2a81d74aa@syzkaller.appspotmail.com
> Fixes: 0df1a55afa83 ("bpf: Warn on internal verifier errors")
>
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
prev parent reply other threads:[~2025-07-31 13:53 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-31 3:19 [syzbot] [bpf?] WARNING in convert_ctx_accesses syzbot
2025-07-31 13:43 ` syzbot
2025-07-31 13:53 ` Paul Chaignon [this message]
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