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Message-ID: <43b7c2c4-9bba-444a-ba27-9a8f3623a953@kernel.dk>
Date: Tue, 13 Aug 2024 06:14:48 -0600
From: Jens Axboe <axboe@...nel.dk>
To: syzbot <syzbot+2b946a3fd80caf971b21@...kaller.appspotmail.com>,
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 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
diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c
index b3722e5275e7..3b50dc9586d1 100644
--- a/io_uring/sqpoll.c
+++ b/io_uring/sqpoll.c
@@ -44,7 +44,7 @@ void io_sq_thread_unpark(struct io_sq_data *sqd)
void io_sq_thread_park(struct io_sq_data *sqd)
__acquires(&sqd->lock)
{
- WARN_ON_ONCE(sqd->thread == current);
+ WARN_ON_ONCE(data_race(sqd->thread) == current);
atomic_inc(&sqd->park_pending);
set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
--
Jens Axboe
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