linux-kernel - Re: INFO: task can't die in io_uring

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Date:   Thu, 3 Sep 2020 10:43:33 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     syzbot <syzbot+3227d097b95b4207b570@...kaller.appspotmail.com>,
        io-uring@...r.kernel.org, keescook@...omium.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        sgarzare@...hat.com, syzkaller-bugs@...glegroups.com,
        viro@...iv.linux.org.uk
Subject: Re: INFO: task can't die in io_uring_setup

On 9/3/20 10:28 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    4442749a Add linux-next specific files for 20200902
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=138e7285900000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=39134fcec6c78e33
> dashboard link: https://syzkaller.appspot.com/bug?extid=3227d097b95b4207b570
> compiler:       gcc (GCC) 10.1.0-syz 20200507
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15306279900000
> 
> The issue was bisected to:
> 
> commit dfe127799f8e663c7e3e48b5275ca538b278177b
> Author: Stefano Garzarella <sgarzare@...hat.com>
> Date:   Thu Aug 27 14:58:31 2020 +0000
> 
>     io_uring: allow disabling rings during the creation
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15b09115900000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=17b09115900000
> console output: https://syzkaller.appspot.com/x/log.txt?x=13b09115900000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+3227d097b95b4207b570@...kaller.appspotmail.com
> Fixes: dfe127799f8e ("io_uring: allow disabling rings during the creation")
> 
> INFO: task syz-executor.0:28543 can't die for more than 143 seconds.
> task:syz-executor.0  state:D stack:28824 pid:28543 ppid:  6864 flags:0x00004004
> Call Trace:
>  context_switch kernel/sched/core.c:3777 [inline]
>  __schedule+0xea9/0x2230 kernel/sched/core.c:4526
>  schedule+0xd0/0x2a0 kernel/sched/core.c:4601
>  schedule_timeout+0x1d8/0x250 kernel/time/timer.c:1855
>  do_wait_for_common kernel/sched/completion.c:85 [inline]
>  __wait_for_common kernel/sched/completion.c:106 [inline]
>  wait_for_common kernel/sched/completion.c:117 [inline]
>  wait_for_completion+0x163/0x260 kernel/sched/completion.c:138
>  io_sq_thread_stop fs/io_uring.c:6906 [inline]
>  io_finish_async fs/io_uring.c:6920 [inline]
>  io_sq_offload_create fs/io_uring.c:7595 [inline]
>  io_uring_create fs/io_uring.c:8671 [inline]
>  io_uring_setup+0x1495/0x29a0 fs/io_uring.c:8744
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9

This very much looks like a dupe of the issue that Hillf already
fixed, but as there's no C reproducer yet, I can't verify.

-- 
Jens Axboe