KCSAN: data-race in __process_echoes / n_tty_write (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9dbc1c03 Merge tag 'xfs-5.10-fixes-3' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=105d6852500000
kernel config: https://syzkaller.appspot.com/x/.config?x=31a046454060d678
dashboard link: https://syzkaller.appspot.com/bug?extid=ffae0a48371a231c9e3b
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [gre...@linuxfoundation.org jiri...@kernel.org linux-...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ffae0a...@syzkaller.appspotmail.com

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

write to 0xffffc90000e65278 of 8 bytes by task 18971 on cpu 1:
__process_echoes+0x603/0x650 drivers/tty/n_tty.c:768
flush_echoes drivers/tty/n_tty.c:829 [inline]
__receive_buf drivers/tty/n_tty.c:1648 [inline]
n_tty_receive_buf_common+0x1b80/0x1df0 drivers/tty/n_tty.c:1742
n_tty_receive_buf2+0x2e/0x40 drivers/tty/n_tty.c:1777
tty_ldisc_receive_buf+0x61/0xf0 drivers/tty/tty_buffer.c:461
tty_port_default_receive_buf+0x54/0x80 drivers/tty/tty_port.c:38
receive_buf drivers/tty/tty_buffer.c:481 [inline]
flush_to_ldisc+0x1c5/0x2b0 drivers/tty/tty_buffer.c:533
process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
worker_thread+0x635/0xb90 kernel/workqueue.c:2418
kthread+0x1fa/0x220 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffffc90000e65278 of 8 bytes by task 20563 on cpu 0:
process_echoes drivers/tty/n_tty.c:806 [inline]
n_tty_write+0x151/0xae0 drivers/tty/n_tty.c:2319
do_tty_write drivers/tty/tty_io.c:962 [inline]
tty_write+0x3fc/0x5e0 drivers/tty/tty_io.c:1046
vfs_write+0x1b9/0x690 fs/read_write.c:603
ksys_write+0xce/0x180 fs/read_write.c:658
__do_sys_write fs/read_write.c:670 [inline]
__se_sys_write fs/read_write.c:667 [inline]
__x64_sys_write+0x3e/0x50 fs/read_write.c:667
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 20563 Comm: syz-executor.4 Not tainted 5.10.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

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