syzbot

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BUG: KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios

read-write to 0xffff888151635108 of 4 bytes by task 30173 on cpu 0:
 unset_locked_termios drivers/tty/tty_ioctl.c:232 [inline]
 tty_set_termios+0xfa/0x8a0 drivers/tty/tty_ioctl.c:359
 set_termios+0x47e/0x4c0 drivers/tty/tty_ioctl.c:534
 tty_mode_ioctl+0x3e1/0x580
 n_tty_ioctl_helper+0x8d/0x240 drivers/tty/tty_ioctl.c:1002
 n_tty_ioctl+0xfd/0x200 drivers/tty/n_tty.c:2499
 tty_ioctl+0x875/0xbc0 drivers/tty/tty_io.c:2795
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xcf/0x140 fs/ioctl.c:856
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888151635108 of 4 bytes by task 24059 on cpu 1:
 n_tty_lookahead_flow_ctrl+0x59/0x120 drivers/tty/n_tty.c:1491
 tty_port_default_lookahead_buf+0x85/0xb0 drivers/tty/tty_port.c:61
 lookahead_bufs drivers/tty/tty_buffer.c:498 [inline]
 flush_to_ldisc+0x30a/0x400 drivers/tty/tty_buffer.c:568
 process_one_work+0x434/0x860 kernel/workqueue.c:2597
 worker_thread+0x5f2/0xa10 kernel/workqueue.c:2748
 kthread+0x1d7/0x210 kernel/kthread.c:389
 ret_from_fork+0x2e/0x40 arch/x86/kernel/process.c:145
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:296

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 24059 Comm: kworker/u4:25 Not tainted 6.5.0-rc3-syzkaller-00275-gffabf7c73176 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
Workqueue: events_unbound flush_to_ldisc
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