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BUG: KCSAN: data-race in n_tty_write / tty_reopen

write to 0xffff88813b7885a8 of 4 bytes by task 30314 on cpu 1:
 tty_reopen+0x114/0x1c0 drivers/tty/tty_io.c:1376
 tty_open_by_driver drivers/tty/tty_io.c:2092 [inline]
 tty_open+0x900/0xb60 drivers/tty/tty_io.c:2146
 chrdev_open+0x39c/0x420 fs/char_dev.c:414
 do_dentry_open+0x529/0x850 fs/open.c:826
 vfs_open+0x43/0x50 fs/open.c:949
 do_open fs/namei.c:3374 [inline]
 path_openat+0x1787/0x1f20 fs/namei.c:3507
 do_filp_open+0xe9/0x200 fs/namei.c:3534
 do_sys_openat2+0xa3/0x250 fs/open.c:1204
 do_sys_open fs/open.c:1220 [inline]
 __do_sys_openat fs/open.c:1236 [inline]
 __se_sys_openat fs/open.c:1231 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1231
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813b7885a8 of 4 bytes by task 30308 on cpu 0:
 n_tty_write+0x2e7/0xaf0 drivers/tty/n_tty.c:2282
 do_tty_write drivers/tty/tty_io.c:1038 [inline]
 file_tty_write+0x409/0x660 drivers/tty/tty_io.c:1110
 tty_write+0x24/0x30 drivers/tty/tty_io.c:1131
 call_write_iter include/linux/fs.h:2114 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x69d/0x770 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000001 -> 0x00000002

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 30308 Comm: syz-executor.2 Tainted: G        W         5.14.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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