[syzbot] [io-uring?] KCSAN: data-race in __flush_work / __flush_work (2)

[syzbot <syzbot+b3e4f2f51ed645fd5df2@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    a5dbd76a8942 Merge tag 'x86-urgent-2024-08-04' of git://gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13d5a373980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d16924117a4f7e9
dashboard link: https://syzkaller.appspot.com/bug?extid=b3e4f2f51ed645fd5df2
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/ba663ad5dbf5/disk-a5dbd76a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/226a427d6581/vmlinux-a5dbd76a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9f982777516a/bzImage-a5dbd76a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b3e4f2f51ed645fd5df2@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __flush_work / __flush_work

write to 0xffff8881223aa3e8 of 8 bytes by task 3998 on cpu 0:
 instrument_write include/linux/instrumented.h:41 [inline]
 ___set_bit include/asm-generic/bitops/instrumented-non-atomic.h:28 [inline]
 insert_wq_barrier kernel/workqueue.c:3790 [inline]
 start_flush_work kernel/workqueue.c:4142 [inline]
 __flush_work+0x30b/0x570 kernel/workqueue.c:4178
 flush_work kernel/workqueue.c:4229 [inline]
 flush_delayed_work+0x66/0x70 kernel/workqueue.c:4251
 io_fallback_tw+0x24b/0x320 io_uring/io_uring.c:1087
 tctx_task_work_run+0xd1/0x1b0 io_uring/io_uring.c:1099
 tctx_task_work+0x40/0x80 io_uring/io_uring.c:1124
 task_work_run+0x13a/0x1a0 kernel/task_work.c:228
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x5dd/0x1720 kernel/exit.c:882
 do_group_exit+0x102/0x150 kernel/exit.c:1031
 get_signal+0xf2f/0x1080 kernel/signal.c:2917
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x59/0x130 kernel/entry/common.c:218
 do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881223aa3e8 of 8 bytes by task 50 on cpu 1:
 __flush_work+0x42a/0x570 kernel/workqueue.c:4188
 flush_work kernel/workqueue.c:4229 [inline]
 flush_delayed_work+0x66/0x70 kernel/workqueue.c:4251
 io_uring_try_cancel_requests+0x35b/0x370 io_uring/io_uring.c:3000
 io_ring_exit_work+0x148/0x500 io_uring/io_uring.c:2779
 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: 0x0000000000400000 -> 0xffff88810006c00d

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 50 Comm: kworker/u8:3 Not tainted 6.11.0-rc1-syzkaller-00334-ga5dbd76a8942 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Workqueue: iou_exit io_ring_exit_work
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup