syzbot

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BUG: KCSAN: data-race in n_tty_write / tty_set_termios

read-write to 0xffff888133329d14 of 4 bytes by task 16770 on cpu 1:
 unset_locked_termios drivers/tty/tty_ioctl.c:234 [inline]
 tty_set_termios+0x1b0/0x8a0 drivers/tty/tty_ioctl.c:358
 set_termios+0x251/0x280 drivers/tty/tty_ioctl.c:517
 tty_mode_ioctl+0x405/0x470
 n_tty_ioctl_helper+0x83/0x340 drivers/tty/tty_ioctl.c:980
 n_tty_ioctl+0xfc/0x1f0 drivers/tty/n_tty.c:2483
 tty_ioctl+0x6e9/0x940 drivers/tty/tty_io.c:2784
 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+0x63/0xcd

read to 0xffff888133329d14 of 4 bytes by task 16763 on cpu 0:
 n_tty_write+0x88/0xb10 drivers/tty/n_tty.c:2327
 do_tty_write drivers/tty/tty_io.c:1018 [inline]
 file_tty_write+0x3b8/0x620 drivers/tty/tty_io.c:1089
 tty_write+0x24/0x30 drivers/tty/tty_io.c:1110
 call_write_iter include/linux/fs.h:2189 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x468/0x760 fs/read_write.c:584
 ksys_write+0xe8/0x1a0 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+0x3e/0x50 fs/read_write.c:646
 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+0x63/0xcd

value changed: 0x00008a3b -> 0x0000585c

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 16763 Comm: syz-executor.4 Not tainted 6.2.0-rc4-syzkaller-00041-gc1649ec55708-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/12/2023
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