syzbot

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BUG: KCSAN: data-race in n_tty_poll / tty_set_termios

write to 0xffff888137e6a91e of 1 bytes by task 5945 on cpu 1:
 unset_locked_termios drivers/tty/tty_ioctl.c:220 [inline]
 tty_set_termios+0x3a4/0x8a0 drivers/tty/tty_ioctl.c:340
 set_termios+0x47e/0x4c0 drivers/tty/tty_ioctl.c:516
 tty_mode_ioctl+0x391/0x5d0
 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:2812
 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:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888137e6a91e of 1 bytes by task 9 on cpu 0:
 input_available_p drivers/tty/n_tty.c:1927 [inline]
 n_tty_poll+0x217/0x490 drivers/tty/n_tty.c:2458
 tty_poll+0x7b/0xf0 drivers/tty/tty_io.c:2214
 vfs_poll include/linux/poll.h:88 [inline]
 p9_fd_poll net/9p/trans_fd.c:237 [inline]
 p9_poll_mux net/9p/trans_fd.c:629 [inline]
 p9_poll_workfn+0x1e9/0x410 net/9p/trans_fd.c:1178
 process_one_work kernel/workqueue.c:2633 [inline]
 process_scheduled_works+0x5b8/0xa40 kernel/workqueue.c:2706
 worker_thread+0x525/0x730 kernel/workqueue.c:2787
 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: 0x79 -> 0xf2

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9 Comm: kworker/0:1 Not tainted 6.8.0-rc2-syzkaller-00084-g5c24e4e9e708 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Workqueue: events p9_poll_workfn
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