[moderation] [serial?] KCSAN: data-race in __tty_hangup / tty_hung_up_p (14)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d358e5254674 Merge tag 'for-6.19/dm-changes' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=133321b4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9230b46da882b43c
dashboard link: https://syzkaller.appspot.com/bug?extid=eaebebd35f33692566a2
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
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/4f60a2fdbe51/disk-d358e525.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/127ec1e804fb/vmlinux-d358e525.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2402e3e45961/bzImage-d358e525.xz

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

==================================================================
BUG: KCSAN: data-race in __tty_hangup / tty_hung_up_p

write to 0xffff88810cbf6d88 of 8 bytes by task 20247 on cpu 1:
__tty_hangup+0x1ef/0x540 drivers/tty/tty_io.c:612
tty_vhangup+0x17/0x20 drivers/tty/tty_io.c:691
pty_close+0x2c5/0x2f0 drivers/tty/pty.c:77
tty_release+0x1ff/0xb10 drivers/tty/tty_io.c:1745
__fput+0x29b/0x650 fs/file_table.c:468
____fput+0x1c/0x30 fs/file_table.c:496
task_work_run+0x131/0x1a0 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
exit_to_user_mode_loop+0x1fe/0x740 kernel/entry/common.c:75
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
do_syscall_64+0x202/0x2a0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810cbf6d88 of 8 bytes by task 20262 on cpu 0:
tty_hung_up_p+0x20/0x50 drivers/tty/tty_io.c:736
n_tty_write+0x2fe/0xbf0 drivers/tty/n_tty.c:2360
iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
file_tty_write+0x378/0x690 drivers/tty/tty_io.c:1081
tty_write+0x25/0x30 drivers/tty/tty_io.c:1102
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x52a/0x960 fs/read_write.c:686
ksys_write+0xda/0x1a0 fs/read_write.c:738
__do_sys_write fs/read_write.c:749 [inline]
__se_sys_write fs/read_write.c:746 [inline]
__x64_sys_write+0x40/0x50 fs/read_write.c:746
x64_sys_call+0x2847/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffffff858a6020 -> 0xffffffff858a5f10

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 20262 Comm: syz.5.5472 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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