[moderation] [io-uring?] KCSAN: data-race in __io_queue_proc / io_poll_wake (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fd95357fd8c6 Merge tag 'sched_ext-for-6.18-rc6-fixes-2' of..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1244aa12580000
kernel config: https://syzkaller.appspot.com/x/.config?x=655255e3ef31c19b
dashboard link: https://syzkaller.appspot.com/bug?extid=120f36735857e19000c8
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [ax...@kernel.dk io-u...@vger.kernel.org linux-...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/667acf2a53a7/disk-fd95357f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/36c22f9efaff/vmlinux-fd95357f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d6a52864f8d0/bzImage-fd95357f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+120f36...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __io_queue_proc / io_poll_wake

write to 0xffff88817b26a428 of 8 bytes by task 1350 on cpu 1:
io_poll_wake+0x1f9/0x3b0 io_uring/poll.c:416
__wake_up_common kernel/sched/wait.c:108 [inline]
__wake_up_common_lock kernel/sched/wait.c:125 [inline]
__wake_up+0x66/0xb0 kernel/sched/wait.c:146
__receive_buf drivers/tty/n_tty.c:1641 [inline]
n_tty_receive_buf_common+0x735/0xbe0 drivers/tty/n_tty.c:1723
n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1769
tty_ldisc_receive_buf+0x66/0xf0 drivers/tty/tty_buffer.c:387
tty_port_default_receive_buf+0x59/0x90 drivers/tty/tty_port.c:37
receive_buf drivers/tty/tty_buffer.c:445 [inline]
flush_to_ldisc+0x148/0x340 drivers/tty/tty_buffer.c:495
process_one_work kernel/workqueue.c:3263 [inline]
process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3346
worker_thread+0x582/0x770 kernel/workqueue.c:3427
kthread+0x489/0x510 kernel/kthread.c:463
ret_from_fork+0x122/0x1b0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88817b26a428 of 8 bytes by task 15675 on cpu 0:
__io_queue_proc+0x10a/0x280 io_uring/poll.c:469
io_async_queue_proc+0x43/0x50 io_uring/poll.c:632
poll_wait include/linux/poll.h:45 [inline]
n_tty_poll+0x7a/0x450 drivers/tty/n_tty.c:2451
tty_poll+0x79/0xf0 drivers/tty/tty_io.c:2199
vfs_poll include/linux/poll.h:82 [inline]
__io_arm_poll_handler+0x1ee/0xb70 io_uring/poll.c:579
io_arm_apoll+0x2e8/0x420 io_uring/poll.c:687
io_arm_poll_handler+0x131/0x160 io_uring/poll.c:716
io_queue_async+0x25d/0x2d0 io_uring/io_uring.c:2055
io_queue_sqe io_uring/io_uring.c:2081 [inline]
io_req_task_submit+0xf6/0x100 io_uring/io_uring.c:1466
io_poll_task_func+0x5fc/0x7c0 io_uring/poll.c:-1
io_handle_tw_list+0xcc/0x1c0 io_uring/io_uring.c:1151
tctx_task_work_run+0x6d/0x1a0 io_uring/io_uring.c:1216
tctx_task_work+0x3f/0x80 io_uring/io_uring.c:1234
task_work_run+0x131/0x1a0 kernel/task_work.c:227
get_signal+0xe12/0xf70 kernel/signal.c:2807
arch_do_signal_or_restart+0x96/0x440 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop+0x77/0x110 kernel/entry/common.c:40
exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff888118df7208 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 15675 Comm: syz.7.16077 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
==================================================================


---
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 syzk...@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