syzbot

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BUG: KCSAN: data-race in __stop_tty / pty_write

write to 0xffff888121d191bc of 1 bytes by task 2812 on cpu 1:
 __stop_tty+0x3e/0x80 drivers/tty/tty_io.c:760
 n_tty_ioctl_helper+0x2bd/0x340 drivers/tty/tty_ioctl.c:874
 n_tty_ioctl+0xfc/0x1f0 drivers/tty/n_tty.c:2483
 tty_ioctl+0x71e/0x970 drivers/tty/tty_io.c:2787
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:856
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888121d191bc of 1 bytes by task 8 on cpu 0:
 pty_write+0x22/0xa0 drivers/tty/pty.c:115
 tty_put_char+0x7f/0xa0 drivers/tty/tty_io.c:3144
 __process_echoes+0x3b9/0x650 drivers/tty/n_tty.c:717
 flush_echoes drivers/tty/n_tty.c:817 [inline]
 __receive_buf drivers/tty/n_tty.c:1615 [inline]
 n_tty_receive_buf_common+0x844/0xbf0 drivers/tty/n_tty.c:1711
 n_tty_receive_buf2+0x2e/0x40 drivers/tty/n_tty.c:1746
 tty_ldisc_receive_buf+0x5b/0xf0 drivers/tty/tty_buffer.c:457
 tty_port_default_receive_buf+0x54/0x80 drivers/tty/tty_port.c:39
 receive_buf drivers/tty/tty_buffer.c:515 [inline]
 flush_to_ldisc+0x1d9/0x470 drivers/tty/tty_buffer.c:565
 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
 worker_thread+0x618/0xa70 kernel/workqueue.c:2436
 kthread+0x1a9/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8 Comm: kworker/u4:0 Not tainted 6.0.0-syzkaller-05118-g833477fce7a1-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
Workqueue: events_unbound flush_to_ldisc
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