syzbot

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BUG: KCSAN: data-race in n_tty_check_unthrottle / n_tty_receive_buf_common

write to 0xffff88813b7daddc of 4 bytes by task 24542 on cpu 1:
 tty_set_flow_change drivers/tty/tty.h:59 [inline]
 n_tty_check_throttle drivers/tty/n_tty.c:253 [inline]
 n_tty_receive_buf_common+0xa6e/0xbc0 drivers/tty/n_tty.c:1748
 n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1769
 tiocsti+0x171/0x1d0 drivers/tty/tty_io.c:2295
 tty_ioctl+0x415/0xbc0 drivers/tty/tty_io.c:2694
 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+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

write to 0xffff88813b7daddc of 4 bytes by task 24543 on cpu 0:
 __tty_set_flow_change drivers/tty/tty.h:53 [inline]
 n_tty_check_unthrottle+0x1a8/0x1c0 drivers/tty/n_tty.c:287
 n_tty_read+0xf0a/0x11c0 drivers/tty/n_tty.c:2302
 iterate_tty_read drivers/tty/tty_io.c:862 [inline]
 tty_read+0x152/0x470 drivers/tty/tty_io.c:937
 call_read_iter include/linux/fs.h:2014 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x3c0/0x590 fs/read_write.c:470
 ksys_read+0xeb/0x1a0 fs/read_write.c:613
 __do_sys_read fs/read_write.c:623 [inline]
 __se_sys_read fs/read_write.c:621 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:621
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000002 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 24543 Comm: syz-executor.1 Not tainted 6.7.0-rc6-syzkaller-00022-g55cb5f43689d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
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