syzbot

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BUG: KCSAN: data-race in n_tty_write / tty_reopen

read-write to 0xffff88813f1e71a8 of 4 bytes by task 1198 on cpu 1:
 tty_reopen+0x10c/0x1b0 drivers/tty/tty_io.c:1367
 tty_open_by_driver drivers/tty/tty_io.c:2078 [inline]
 tty_open+0x8f4/0xb00 drivers/tty/tty_io.c:2131
 chrdev_open+0x322/0x390 fs/char_dev.c:414
 do_dentry_open+0x635/0xbd0 fs/open.c:948
 vfs_open+0x4a/0x50 fs/open.c:1082
 do_open fs/namei.c:3622 [inline]
 path_openat+0x1819/0x1d70 fs/namei.c:3779
 do_filp_open+0xf6/0x200 fs/namei.c:3809
 do_sys_openat2+0xab/0x110 fs/open.c:1440
 do_sys_open fs/open.c:1455 [inline]
 __do_sys_openat fs/open.c:1471 [inline]
 __se_sys_openat fs/open.c:1466 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1466
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88813f1e71a8 of 4 bytes by task 1196 on cpu 0:
 n_tty_write+0x321/0xb60 drivers/tty/n_tty.c:2373
 iterate_tty_write drivers/tty/tty_io.c:1021 [inline]
 file_tty_write+0x382/0x680 drivers/tty/tty_io.c:1092
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1113
 call_write_iter include/linux/fs.h:2020 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x48a/0x790 fs/read_write.c:584
 ksys_write+0xeb/0x1a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000001 -> 0x00000002

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1196 Comm: syz-executor.2 Not tainted 6.7.0-rc2-syzkaller-00195-g0f5cc96c367f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
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