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BUG: KCSAN: data-race in n_tty_receive_char_flow_ctrl / tty_set_termios

write to 0xffff888153941922 of 1 bytes by task 27534 on cpu 1:
 unset_locked_termios drivers/tty/tty_ioctl.c:220 [inline]
 tty_set_termios+0x4c8/0x8a0 drivers/tty/tty_ioctl.c:340
 set_termios+0x355/0x4c0 drivers/tty/tty_ioctl.c:520
 tty_mode_ioctl+0x3e1/0x590
 n_tty_ioctl_helper+0x8d/0x240 drivers/tty/tty_ioctl.c:986
 n_tty_ioctl+0xfd/0x200 drivers/tty/n_tty.c:2511
 tty_ioctl+0x875/0xbc0 drivers/tty/tty_io.c:2789
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xcf/0x140 fs/ioctl.c:857
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:857
 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 0xffff888153941922 of 1 bytes by task 11484 on cpu 0:
 n_tty_is_char_flow_ctrl drivers/tty/n_tty.c:1220 [inline]
 n_tty_receive_char_flow_ctrl+0x58/0x190 drivers/tty/n_tty.c:1241
 n_tty_lookahead_flow_ctrl+0xee/0x130 drivers/tty/n_tty.c:1516
 tty_port_default_lookahead_buf+0x87/0xb0 drivers/tty/tty_port.c:59
 lookahead_bufs drivers/tty/tty_buffer.c:427 [inline]
 flush_to_ldisc+0x30c/0x400 drivers/tty/tty_buffer.c:497
 process_one_work kernel/workqueue.c:2630 [inline]
 process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703
 worker_thread+0x525/0x730 kernel/workqueue.c:2784
 kthread+0x1d7/0x210 kernel/kthread.c:388
 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

value changed: 0x13 -> 0x47

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11484 Comm: kworker/u4:9 Not tainted 6.7.0-rc3-syzkaller-00298-g1b8af6552cb7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
Workqueue: events_unbound flush_to_ldisc
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