[moderation] [serial?] KCSAN: data-race in n_tty_receive_signal_char / n_tty_write (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8d3dea210042 Merge tag 'mips-fixes_6.8_2' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11f751fc180000
kernel config: https://syzkaller.appspot.com/x/.config?x=b4c8befe72e5ccb8
dashboard link: https://syzkaller.appspot.com/bug?extid=441a63d35c886ed5dacf
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/2525e543177e/disk-8d3dea21.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/001d79f4ac56/vmlinux-8d3dea21.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f0e98e0c0962/bzImage-8d3dea21.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+441a63...@syzkaller.appspotmail.com

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

write to 0xffffc9000a547028 of 8 bytes by task 2422 on cpu 1:
commit_echoes drivers/tty/n_tty.c:758 [inline]
n_tty_receive_signal_char+0x2eb/0x3e0 drivers/tty/n_tty.c:1213
n_tty_receive_buf_standard+0x6b6/0x2e20 drivers/tty/n_tty.c:1604
__receive_buf drivers/tty/n_tty.c:1630 [inline]
n_tty_receive_buf_common+0x7e5/0xbc0 drivers/tty/n_tty.c:1729
n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1775
tty_ldisc_receive_buf+0x60/0xe0 drivers/tty/tty_buffer.c:386
tty_port_default_receive_buf+0x59/0x90 drivers/tty/tty_port.c:37
receive_buf drivers/tty/tty_buffer.c:444 [inline]
flush_to_ldisc+0x1ca/0x400 drivers/tty/tty_buffer.c:494
process_one_work kernel/workqueue.c:2633 [inline]
process_scheduled_works+0x5b8/0xa40 kernel/workqueue.c:2706
worker_thread+0x525/0x730 kernel/workqueue.c:2787
kthread+0x1d7/0x210 kernel/kthread.c:388
ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

read to 0xffffc9000a547028 of 8 bytes by task 13735 on cpu 0:
process_echoes drivers/tty/n_tty.c:784 [inline]
n_tty_write+0x161/0xb60 drivers/tty/n_tty.c:2365
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: 0x0000000000000000 -> 0x000000000000003d

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 13735 Comm: syz-executor.1 Not tainted 6.8.0-rc4-syzkaller-00034-g8d3dea210042 #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.