[moderation] [serial?] KCSAN: data-race in __stop_tty / n_tty_receive_char (10)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2961f841b025 Merge tag 'turbostat-2026.02.14' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1499315a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=70c3ed59b49365c3
dashboard link: https://syzkaller.appspot.com/bug?extid=80594a852f796415b1ae
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [gre...@linuxfoundation.org jiri...@kernel.org linux-...@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/d46d093103b7/disk-2961f841.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/65389ddd6772/vmlinux-2961f841.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f9ef596dd3b2/bzImage-2961f841.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+80594a...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __stop_tty / n_tty_receive_char

write to 0xffff88810bad45bc of 1 bytes by task 27089 on cpu 1:
__stop_tty+0x36/0x90 drivers/tty/tty_io.c:744
n_tty_ioctl_helper+0x2d1/0x370 drivers/tty/tty_ioctl.c:951
n_tty_ioctl+0x101/0x230 drivers/tty/n_tty.c:2496
tty_ioctl+0x83e/0xb80 drivers/tty/tty_io.c:2801
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
x64_sys_call+0x1563/0x3020 arch/x86/include/generated/asm/syscalls_64.h:17
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810bad45bc of 1 bytes by task 307 on cpu 0:
n_tty_receive_char+0x3d/0x6d0 drivers/tty/n_tty.c:1403
n_tty_receive_buf_standard+0x552/0x3f60 drivers/tty/n_tty.c:1582
__receive_buf drivers/tty/n_tty.c:1616 [inline]
n_tty_receive_buf_common+0x7f3/0xc10 drivers/tty/n_tty.c:1715
n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1759
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:3275 [inline]
process_scheduled_works+0x4de/0x9e0 kernel/workqueue.c:3358
worker_thread+0x581/0x770 kernel/workqueue.c:3439
kthread+0x22a/0x280 kernel/kthread.c:467
ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 307 Comm: kworker/u8:5 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: events_unbound flush_to_ldisc
==================================================================


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