[moderation] [serial?] KCSAN: data-race in n_tty_close / pty_close (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4f5e5092fdbf Merge tag 'net-6.8-rc5' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14e84784180000
kernel config: https://syzkaller.appspot.com/x/.config?x=b4c8befe72e5ccb8
dashboard link: https://syzkaller.appspot.com/bug?extid=e729068abc53bcccc1df
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/517fa88c8613/disk-4f5e5092.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cf7004696e01/vmlinux-4f5e5092.xz
kernel image: https://storage.googleapis.com/syzbot-assets/048b9047e0d5/bzImage-4f5e5092.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e72906...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in n_tty_close / pty_close

write to 0xffff8881570195d5 of 1 bytes by task 14559 on cpu 0:
pty_close+0x124/0x280 drivers/tty/pty.c:61
tty_release+0x204/0x930 drivers/tty/tty_io.c:1760
__fput+0x299/0x630 fs/file_table.c:376
____fput+0x15/0x20 fs/file_table.c:404
task_work_run+0x135/0x1a0 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:108 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:201 [inline]
syscall_exit_to_user_mode+0xbd/0x130 kernel/entry/common.c:212
do_syscall_64+0xda/0x1d0 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff8881570195d5 of 1 bytes by task 14562 on cpu 1:
n_tty_packet_mode_flush drivers/tty/n_tty.c:335 [inline]
n_tty_close+0x58/0x130 drivers/tty/n_tty.c:1886
tty_ldisc_close drivers/tty/tty_ldisc.c:455 [inline]
tty_ldisc_kill+0x8d/0x130 drivers/tty/tty_ldisc.c:607
tty_ldisc_hangup+0x2e0/0x360 drivers/tty/tty_ldisc.c:723
__tty_hangup+0x3c6/0x530 drivers/tty/tty_io.c:630
tty_vhangup drivers/tty/tty_io.c:700 [inline]
tty_ioctl+0x60a/0xbc0 drivers/tty/tty_io.c:2743
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

value changed: 0x01 -> 0x00

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14562 Comm: syz-executor.1 Not tainted 6.8.0-rc4-syzkaller-00180-g4f5e5092fdbf #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.