syzbot

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BUG: KCSAN: data-race in pty_write_room / tty_send_xchar

write to 0xffff88812283e1bc of 1 bytes by task 24558 on cpu 1:
 __stop_tty drivers/tty/tty_io.c:753 [inline]
 stop_tty drivers/tty/tty_io.c:777 [inline]
 tty_send_xchar+0x1d4/0x280 drivers/tty/tty_io.c:1163
 n_tty_ioctl_helper+0x1dd/0x240
 n_tty_ioctl+0xfd/0x200 drivers/tty/n_tty.c:2516
 tty_ioctl+0x875/0xbc0 drivers/tty/tty_io.c:2785
 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:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88812283e1bc of 1 bytes by task 463 on cpu 0:
 pty_write_room+0x1c/0x70 drivers/tty/pty.c:131
 tty_write_room+0x38/0x50 drivers/tty/tty_ioctl.c:73
 __process_echoes+0x36/0x6a0 drivers/tty/n_tty.c:708
 flush_echoes drivers/tty/n_tty.c:812 [inline]
 __receive_buf drivers/tty/n_tty.c:1637 [inline]
 n_tty_receive_buf_common+0x8e6/0xbc0 drivers/tty/n_tty.c:1734
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1780
 tty_ldisc_receive_buf+0x60/0xe0 drivers/tty/tty_buffer.c:387
 tty_port_default_receive_buf+0x59/0x90 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:445 [inline]
 flush_to_ldisc+0x1ca/0x400 drivers/tty/tty_buffer.c:495
 process_one_work kernel/workqueue.c:2630 [inline]
 process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703
 worker_thread+0x525/0x730 kernel/workqueue.c:2784
 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:304

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 463 Comm: kworker/u4:4 Not tainted 6.6.0-rc2-syzkaller-00018-g2cf0f7156238 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
Workqueue: events_unbound flush_to_ldisc
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