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BUG: KCSAN: data-race in ppp_asynctty_receive / tty_set_termios

write to 0xffff8881365cbd22 of 1 bytes by task 6416 on cpu 1:
 unset_locked_termios drivers/tty/tty_ioctl.c:238 [inline]
 tty_set_termios+0x4c8/0x8a0 drivers/tty/tty_ioctl.c:359
 set_termios+0x47e/0x4c0 drivers/tty/tty_ioctl.c:534
 tty_mode_ioctl+0x3e1/0x580
 ppp_asynctty_ioctl+0x21d/0x2e0 drivers/net/ppp/ppp_async.c:324
 tty_ioctl+0x86f/0xbc0 drivers/tty/tty_io.c:2786
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xc9/0x140 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 0xffff8881365cbd22 of 1 bytes by task 34 on cpu 0:
 ppp_async_input drivers/net/ppp/ppp_async.c:913 [inline]
 ppp_asynctty_receive+0x871/0x1040 drivers/net/ppp/ppp_async.c:349
 tty_ldisc_receive_buf+0xbb/0xe0 drivers/tty/tty_buffer.c:461
 tty_port_default_receive_buf+0x58/0x80 drivers/tty/tty_port.c:39
 receive_buf drivers/tty/tty_buffer.c:515 [inline]
 flush_to_ldisc+0x1ca/0x400 drivers/tty/tty_buffer.c:565
 process_one_work+0x3e6/0x750 kernel/workqueue.c:2405
 worker_thread+0x5f2/0xa10 kernel/workqueue.c:2552
 kthread+0x1d7/0x210 kernel/kthread.c:379
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

value changed: 0x13 -> 0x95

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 34 Comm: kworker/u4:2 Not tainted 6.4.0-rc6-syzkaller-00037-gb6dad5178cea #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Workqueue: events_unbound flush_to_ldisc
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