From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Leon Hwang <hffilwlqm@gmail.com>
Cc: syzbot <syzbot+fa5c2814795b5adca240@syzkaller.appspotmail.com>,
Andrii Nakryiko <andrii@kernel.org>,
Alexei Starovoitov <ast@kernel.org>, bpf <bpf@vger.kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Eduard <eddyz87@gmail.com>, Hao Luo <haoluo@google.com>,
John Fastabend <john.fastabend@gmail.com>,
Jiri Olsa <jolsa@kernel.org>, KP Singh <kpsingh@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Network Development <netdev@vger.kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>, Song Liu <song@kernel.org>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
Yonghong Song <yonghong.song@linux.dev>
Subject: Re: [syzbot] [bpf?] possible deadlock in __bpf_ringbuf_reserve (2)
Date: Mon, 25 Aug 2025 19:23:50 -0700 [thread overview]
Message-ID: <CAADnVQ+p76vYLjs9zivq694PSqiPPjv7LJOSXCHsLGuMwgG1jw@mail.gmail.com> (raw)
In-Reply-To: <50f069c5-d962-4743-a8b0-dc1bc4811599@gmail.com>
On Mon, Aug 25, 2025 at 7:20 PM Leon Hwang <hffilwlqm@gmail.com> wrote:
>
>
>
> On 26/8/25 01:39, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: dd9de524183a xsk: Fix immature cq descriptor production
> > git tree: bpf
> > console output: https://syzkaller.appspot.com/x/log.txt?x=102da862580000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=c321f33e4545e2a1
> > dashboard link: https://syzkaller.appspot.com/bug?extid=fa5c2814795b5adca240
> > compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=142da862580000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1588aef0580000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/5a3389c1558f/disk-dd9de524.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/c97133192a27/vmlinux-dd9de524.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/3ae5a1a88637/bzImage-dd9de524.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+fa5c2814795b5adca240@syzkaller.appspotmail.com
> >
> > ============================================
> > WARNING: possible recursive locking detected
> > syzkaller #0 Not tainted
> > --------------------------------------------
> > syz-execprog/5866 is trying to acquire lock:
> > ffffc900048c10d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x1c7/0x5a0 kernel/bpf/ringbuf.c:423
> >
> > but task is already holding lock:
> > ffffc900048e90d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x1c7/0x5a0 kernel/bpf/ringbuf.c:423
> >
> > other info that might help us debug this:
> > Possible unsafe locking scenario:
> >
> > CPU0
> > ----
> > lock(&rb->spinlock);
> > lock(&rb->spinlock);
> >
> > *** DEADLOCK ***
> >
> > May be due to missing lock nesting notation
>
> Confirmed.
>
> I can reproduce this deadlock issue and will work on a fix.
Don't.
It's due to revert.
Once rqspinlock is fixed the revert will be reverted.
next prev parent reply other threads:[~2025-08-26 2:24 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-25 17:39 [syzbot] [bpf?] possible deadlock in __bpf_ringbuf_reserve (2) syzbot
2025-08-26 2:20 ` Leon Hwang
2025-08-26 2:23 ` Alexei Starovoitov [this message]
2025-08-26 2:30 ` Leon Hwang
2025-09-01 22:10 ` syzbot
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