syzbot

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BUG: KCSAN: data-race in fasync_remove_entry / n_tty_write

read to 0xffff8881017e1e40 of 4 bytes by task 8810 on cpu 0:
 n_tty_write+0x8ad/0x9f0 drivers/tty/n_tty.c:2370
 do_tty_write drivers/tty/tty_io.c:962 [inline]
 tty_write+0x2fb/0x4e0 drivers/tty/tty_io.c:1046
 __vfs_write+0x67/0xc0 fs/read_write.c:494
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8881017e1e40 of 4 bytes by task 8805 on cpu 1:
 fasync_remove_entry+0xec/0x120 fs/fcntl.c:884
 fasync_helper+0xcf/0xdc fs/fcntl.c:981
 __tty_fasync+0xae/0x1f0 drivers/tty/tty_io.c:2130
 __tty_hangup+0x162/0x460 drivers/tty/tty_io.c:615
 tty_vhangup+0x21/0x30 drivers/tty/tty_io.c:698
 pty_close+0x25b/0x2d0 drivers/tty/pty.c:79
 tty_release+0x285/0x910 drivers/tty/tty_io.c:1683
 __fput+0x1e1/0x520 fs/file_table.c:280
 ____fput+0x1f/0x30 fs/file_table.c:313
 task_work_run+0xf6/0x130 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2b4/0x2c0 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
 do_syscall_64+0x384/0x3a0 arch/x86/entry/common.c:304
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8805 Comm: syz-executor.1 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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