[moderation] [serial?] KCSAN: data-race in __stop_tty / n_tty_receive_char (8)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 77a903cd8e5a MAINTAINERS: powerpc: Update my status
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=155651df980000
kernel config: https://syzkaller.appspot.com/x/.config?x=9ab3e6c069ff12aa
dashboard link: https://syzkaller.appspot.com/bug?extid=9ea50b519d7d00b2c52b
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
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/c1f988937299/disk-77a903cd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c102e69cfb90/vmlinux-77a903cd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e7f61d7c13ee/bzImage-77a903cd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9ea50b...@syzkaller.appspotmail.com

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

write to 0xffff8881285a2dbc of 1 bytes by task 19565 on cpu 0:
__stop_tty+0x42/0x90 drivers/tty/tty_io.c:747
n_tty_ioctl_helper+0x223/0x240 drivers/tty/tty_ioctl.c:955
n_tty_ioctl+0xfd/0x200 drivers/tty/n_tty.c:2521
tty_ioctl+0x87a/0xbe0 drivers/tty/tty_io.c:2812
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:906 [inline]
__se_sys_ioctl+0xc9/0x140 fs/ioctl.c:892
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
x64_sys_call+0x1690/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:17
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881285a2dbc of 1 bytes by task 18930 on cpu 1:
n_tty_receive_char+0x3d/0x680 drivers/tty/n_tty.c:1427
n_tty_receive_buf_standard+0x4bd/0x2e30 drivers/tty/n_tty.c:1606
__receive_buf drivers/tty/n_tty.c:1640 [inline]
n_tty_receive_buf_common+0x83a/0xbe0 drivers/tty/n_tty.c:1739
n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1785
tty_ldisc_receive_buf+0x63/0x100 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+0x1ce/0x410 drivers/tty/tty_buffer.c:495
process_one_work kernel/workqueue.c:3236 [inline]
process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3317
worker_thread+0x51d/0x6f0 kernel/workqueue.c:3398
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: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 18930 Comm: kworker/u8:9 Not tainted 6.13.0-rc6-syzkaller-00231-g77a903cd8e5a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: events_unbound flush_to_ldisc
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.