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BUG: KCSAN: data-race in isig / pty_close

write to 0xffff8881391f09d9 of 1 bytes by task 16797 on cpu 0:
 pty_close+0x120/0x280 drivers/tty/pty.c:61
 tty_release+0x255/0x9d0 drivers/tty/tty_io.c:1758
 __fput+0x292/0x510 fs/file_table.c:317
 ____fput+0x11/0x20 fs/file_table.c:350
 task_work_run+0x8e/0x110 kernel/task_work.c:164
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0x124/0x130 kernel/entry/common.c:169
 exit_to_user_mode_prepare kernel/entry/common.c:201 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x6a/0x90 kernel/entry/common.c:294
 do_syscall_64+0x37/0x70 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881391f09d9 of 1 bytes by task 16819 on cpu 1:
 n_tty_packet_mode_flush drivers/tty/n_tty.c:342 [inline]
 isig+0x1b4/0x270 drivers/tty/n_tty.c:1123
 n_tty_receive_signal_char drivers/tty/n_tty.c:1213 [inline]
 n_tty_receive_char_special drivers/tty/n_tty.c:1241 [inline]
 n_tty_receive_buf_standard drivers/tty/n_tty.c:1530 [inline]
 __receive_buf drivers/tty/n_tty.c:1549 [inline]
 n_tty_receive_buf_common+0x12ba/0x4c40 drivers/tty/n_tty.c:1645
 n_tty_receive_buf+0x2b/0x40 drivers/tty/n_tty.c:1674
 tiocsti+0x14b/0x1a0 drivers/tty/tty_io.c:2293
 tty_ioctl+0x279/0x970 drivers/tty/tty_io.c:2692
 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+0x44/0xae

value changed: 0x01 -> 0x00

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16819 Comm: syz-executor.3 Tainted: G        W         5.18.0-rc7-syzkaller-00006-g210e04ff7681-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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