syzbot

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BUG: KCSAN: data-race in n_tty_write / tty_set_termios

read-write to 0xffff888179576914 of 4 bytes by task 9120 on cpu 0:
 unset_locked_termios drivers/tty/tty_ioctl.c:233 [inline]
 tty_set_termios+0x1b0/0x8a0 drivers/tty/tty_ioctl.c:357
 set_termios+0x388/0x3c0 drivers/tty/tty_ioctl.c:442
 tty_mode_ioctl+0x4fa/0x5d0
 n_tty_ioctl_helper+0x83/0x340 drivers/tty/tty_ioctl.c:905
 n_tty_ioctl+0xfc/0x1f0 drivers/tty/n_tty.c:2483
 tty_ioctl+0x71e/0x970 drivers/tty/tty_io.c:2787
 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 0xffff888179576914 of 4 bytes by task 9118 on cpu 1:
 n_tty_write+0x88/0xb10 drivers/tty/n_tty.c:2327
 do_tty_write drivers/tty/tty_io.c:1024 [inline]
 file_tty_write+0x3f9/0x650 drivers/tty/tty_io.c:1095
 tty_write+0x24/0x30 drivers/tty/tty_io.c:1116
 call_write_iter include/linux/fs.h:2187 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x468/0x760 fs/read_write.c:578
 ksys_write+0xe8/0x1a0 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write fs/read_write.c:640 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:640
 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 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 9118 Comm: syz-executor.0 Not tainted 6.0.0-rc1-syzkaller-00066-g3b06a2755758-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
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