[moderation] [serial?] KCSAN: data-race in __stop_tty / do_con_write (9)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 45ec2f5f6ed3 Merge tag 'mtd/fixes-for-6.8-rc7' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11f83a32180000
kernel config: https://syzkaller.appspot.com/x/.config?x=53006d590acdf777
dashboard link: https://syzkaller.appspot.com/bug?extid=d50b91c25f8ad1b6edc4
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/b99c38992fd6/disk-45ec2f5f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/be66849a660f/vmlinux-45ec2f5f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f3ca66323870/bzImage-45ec2f5f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d50b91...@syzkaller.appspotmail.com

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

write to 0xffff8881395aa5bc of 1 bytes by task 26991 on cpu 0:
__stop_tty+0x42/0x90 drivers/tty/tty_io.c:753
n_tty_ioctl_helper+0x21f/0x240 drivers/tty/tty_ioctl.c:955
n_tty_ioctl+0xfd/0x200 drivers/tty/n_tty.c:2511
tty_ioctl+0x875/0xbc0 drivers/tty/tty_io.c:2812
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xcf/0x140 fs/ioctl.c:857
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff8881395aa5bc of 1 bytes by task 26975 on cpu 1:
do_con_write+0x179/0x35d0 drivers/tty/vt/vt.c:2885
con_write+0x26/0x40 drivers/tty/vt/vt.c:3251
process_output_block drivers/tty/n_tty.c:574 [inline]
n_tty_write+0x84a/0xb60 drivers/tty/n_tty.c:2379
iterate_tty_write drivers/tty/tty_io.c:1021 [inline]
file_tty_write+0x382/0x680 drivers/tty/tty_io.c:1096
tty_write+0x28/0x30 drivers/tty/tty_io.c:1117
do_iter_readv_writev+0x2b0/0x330
vfs_writev+0x2e9/0x860 fs/read_write.c:971
do_writev+0xf8/0x220 fs/read_write.c:1018
__do_sys_writev fs/read_write.c:1091 [inline]
__se_sys_writev fs/read_write.c:1088 [inline]
__x64_sys_writev+0x45/0x50 fs/read_write.c:1088
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 26975 Comm: syz-executor.2 Not tainted 6.8.0-rc6-syzkaller-00011-g45ec2f5f6ed3 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
==================================================================


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[syzbot]

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