linux-kernel - Re: [syzbot] [io-uring?] KCSAN: data-race in io_sq_thread / io_sq_thread

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Message-ID: <d3cc7fd4-b787-457a-9d90-7db14700a319@kernel.dk>
Date: Tue, 13 Aug 2024 06:17:35 -0600
From: Jens Axboe <axboe@...nel.dk>
To: syzbot <syzbot+2b946a3fd80caf971b21@...kaller.appspotmail.com>
Cc: asml.silence@...il.com, io-uring@...r.kernel.org,
 linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [io-uring?] KCSAN: data-race in io_sq_thread /
 io_sq_thread_park (9)

On Tue, Aug 13, 2024 at 6:14?AM syzbot <syzbot+2b946a3fd80caf971b21@...kaller.appspotmail.com> wrote:
>
> > On 8/13/24 2:50 AM, syzbot wrote:
> >> Hello,
> >>
> >> syzbot found the following issue on:
> >>
> >> HEAD commit:    6a0e38264012 Merge tag 'for-6.11-rc2-tag' of git://git.ker..
> >> git tree:       upstream
> >> console output: https://syzkaller.appspot.com/x/log.txt?x=1019759d980000
> >> kernel config:  https://syzkaller.appspot.com/x/.config?x=cb57e6ebf675f9d2
> >> dashboard link: https://syzkaller.appspot.com/bug?extid=2b946a3fd80caf971b21
> >> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> >>
> >> Unfortunately, I don't have any reproducer for this issue yet.
> >>
> >> Downloadable assets:
> >> disk image: https://storage.googleapis.com/syzbot-assets/753a842a966b/disk-6a0e3826.raw.xz
> >> vmlinux: https://storage.googleapis.com/syzbot-assets/e12e23519777/vmlinux-6a0e3826.xz
> >> kernel image: https://storage.googleapis.com/syzbot-assets/bce0584a8cb4/bzImage-6a0e3826.xz
> >>
> >> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> >> Reported-by: syzbot+2b946a3fd80caf971b21@...kaller.appspotmail.com
> >>
> >> ==================================================================
> >> BUG: KCSAN: data-race in io_sq_thread / io_sq_thread_park
> >>
> >> write to 0xffff888111459638 of 8 bytes by task 10761 on cpu 1:
> >>  io_sq_thread+0xdab/0xff0 io_uring/sqpoll.c:383
> >>  ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
> >>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >>
> >> read to 0xffff888111459638 of 8 bytes by task 10329 on cpu 0:
> >>  io_sq_thread_park+0x1b/0x80 io_uring/sqpoll.c:47
> >>  io_ring_exit_work+0x197/0x500 io_uring/io_uring.c:2786
> >>  process_one_work kernel/workqueue.c:3231 [inline]
> >>  process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3312
> >>  worker_thread+0x526/0x700 kernel/workqueue.c:3390
> >>  kthread+0x1d1/0x210 kernel/kthread.c:389
> >>  ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
> >>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >>
> >> value changed: 0xffff8881223d0000 -> 0x0000000000000000
> >
> > It's just a debug check.
> >
> > #syz test
>
> This crash does not have a reproducer. I cannot test it.

#syz fix: io_uring/sqpoll: annotate debug task == current with data_race()

-- 
Jens Axboe