KCSAN: data-race in pty_close / pty

Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in pty_close / pty_stop serial				1	1056d	1056d	0/26	auto-closed as invalid on 2021/07/07 05:07

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BUG: KCSAN: data-race in pty_close / pty_stop

write to 0xffff888128bfc1d9 of 1 bytes by task 10893 on cpu 0:
 pty_close+0x120/0x2a0 drivers/tty/pty.c:61
 tty_release+0x255/0xa10 drivers/tty/tty_io.c:1771
 __fput+0x295/0x520 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0xae/0x130 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x156/0x190 kernel/entry/common.c:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:300
 do_syscall_64+0x50/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888128bfc1d9 of 1 bytes by task 10907 on cpu 1:
 pty_stop+0x3d/0xe0 drivers/tty/pty.c:349
 __stop_tty drivers/tty/tty_io.c:770 [inline]
 stop_tty drivers/tty/tty_io.c:794 [inline]
 tty_send_xchar+0x20e/0x290 drivers/tty/tty_io.c:1184
 n_tty_ioctl_helper+0x27f/0x4c0
 n_tty_ioctl+0x102/0x200 drivers/tty/n_tty.c:2421
 tty_ioctl+0xaf9/0x11a0 drivers/tty/tty_io.c:2814
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:860
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x01 -> 0x00

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10907 Comm: syz-executor.0 Not tainted 5.15.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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