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BUG: KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios

read-write to 0xffff888104e29108 of 4 bytes by task 6074 on cpu 0:
 unset_locked_termios drivers/tty/tty_ioctl.c:231 [inline]
 tty_set_termios+0xfb/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:2780
 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 0xffff888104e29108 of 4 bytes by task 45 on cpu 1:
 n_tty_lookahead_flow_ctrl+0x63/0x2f0 drivers/tty/n_tty.c:1492
 tty_port_default_lookahead_buf+0x81/0xb0 drivers/tty/tty_port.c:61
 lookahead_bufs drivers/tty/tty_buffer.c:498 [inline]
 flush_to_ldisc+0x33e/0x470 drivers/tty/tty_buffer.c:568
 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
 worker_thread+0x618/0xa70 kernel/workqueue.c:2436
 kthread+0x1a9/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

value changed: 0x00000000 -> 0xfffffff9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 45 Comm: kworker/u4:3 Not tainted 6.1.0-rc1-syzkaller-00158-g440b7895c990-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022
Workqueue: events_unbound flush_to_ldisc
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