[moderation] [serial?] KCSAN: data-race in n_tty_write / tty_release (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3c999d1ae3c7 Merge tag 'wq-for-6.10' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10f896f4980000
kernel config: https://syzkaller.appspot.com/x/.config?x=41b6b83a95ebb268
dashboard link: https://syzkaller.appspot.com/bug?extid=7916a2967e7c7a30b3d9
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/3202939b3e7a/disk-3c999d1a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/95266f6b0d61/vmlinux-3c999d1a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0484a1ee0e68/bzImage-3c999d1a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7916a2...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in n_tty_write / tty_release

read-write to 0xffff88811611eda8 of 4 bytes by task 5372 on cpu 1:
tty_release+0x60a/0x940 drivers/tty/tty_io.c:1821
__fput+0x2c1/0x660 fs/file_table.c:422
____fput+0x15/0x20 fs/file_table.c:450
task_work_run+0x13a/0x1a0 kernel/task_work.c:180
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:114 [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+0xbe/0x130 kernel/entry/common.c:218
do_syscall_64+0xda/0x1d0 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811611eda8 of 4 bytes by task 5369 on cpu 0:
n_tty_write+0x329/0xb90 drivers/tty/n_tty.c:2373
iterate_tty_write drivers/tty/tty_io.c:1021 [inline]
file_tty_write+0x386/0x690 drivers/tty/tty_io.c:1096
tty_write+0x28/0x30 drivers/tty/tty_io.c:1117
call_write_iter include/linux/fs.h:2120 [inline]
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0x765/0x8e0 fs/read_write.c:590
ksys_write+0xeb/0x1b0 fs/read_write.c:643
__do_sys_write fs/read_write.c:655 [inline]
__se_sys_write fs/read_write.c:652 [inline]
__x64_sys_write+0x42/0x50 fs/read_write.c:652
x64_sys_call+0x27b7/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:2
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+0x77/0x7f

value changed: 0x00000002 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5369 Comm: syz-executor.3 Not tainted 6.9.0-syzkaller-07726-g3c999d1ae3c7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
==================================================================


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[syzbot]

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