KCSAN: data-race in n_tty_receive_char_inline / n_tty_receive_char_inline

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: aae5ab85 Merge tag 'riscv-for-linus-5.10-rc6' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16ae9795500000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9b19d1bde60f8d
dashboard link: https://syzkaller.appspot.com/bug?extid=ae21a27816f424fd3dda
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+ae21a2...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in n_tty_receive_char_inline / n_tty_receive_char_inline

write to 0xffffc900037bf000 of 8 bytes by task 4910 on cpu 1:
put_tty_queue drivers/tty/n_tty.c:320 [inline]
n_tty_receive_char_inline+0x630/0x650 drivers/tty/n_tty.c:1426
n_tty_receive_buf_standard drivers/tty/n_tty.c:1583 [inline]
__receive_buf drivers/tty/n_tty.c:1646 [inline]
n_tty_receive_buf_common+0x1892/0x1df0 drivers/tty/n_tty.c:1742
n_tty_receive_buf+0x2b/0x40 drivers/tty/n_tty.c:1771
tiocsti drivers/tty/tty_io.c:2198 [inline]
tty_ioctl+0x8e4/0xfd0 drivers/tty/tty_io.c:2572
vfs_ioctl fs/ioctl.c:48 [inline]
__do_sys_ioctl fs/ioctl.c:753 [inline]
__se_sys_ioctl+0xcb/0x140 fs/ioctl.c:739
__x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:739
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffc900037bf000 of 8 bytes by task 29230 on cpu 0:
put_tty_queue drivers/tty/n_tty.c:319 [inline]
n_tty_receive_char_inline+0x60a/0x650 drivers/tty/n_tty.c:1426
n_tty_receive_buf_standard drivers/tty/n_tty.c:1583 [inline]
__receive_buf drivers/tty/n_tty.c:1646 [inline]
n_tty_receive_buf_common+0x1892/0x1df0 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+0x1fd/0x220 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 29230 Comm: kworker/u4:6 Not tainted 5.10.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_unbound flush_to_ldisc
==================================================================


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[syzbot]

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