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BUG: KCSAN: data-race in n_tty_check_unthrottle / n_tty_receive_buf_common

write to 0xffff88813998a1e8 of 4 bytes by task 11601 on cpu 1:
 tty_set_flow_change drivers/tty/tty.h:54 [inline]
 n_tty_check_unthrottle+0xe8/0x1d0 drivers/tty/n_tty.c:291
 n_tty_read+0xe07/0x1070 drivers/tty/n_tty.c:2214
 iterate_tty_read drivers/tty/tty_io.c:868 [inline]
 tty_read+0x19c/0x430 drivers/tty/tty_io.c:944
 call_read_iter include/linux/fs.h:2156 [inline]
 new_sync_read fs/read_write.c:400 [inline]
 vfs_read+0x66c/0x750 fs/read_write.c:481
 ksys_read+0xd9/0x190 fs/read_write.c:619
 __do_sys_read fs/read_write.c:629 [inline]
 __se_sys_read fs/read_write.c:627 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:627
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

write to 0xffff88813998a1e8 of 4 bytes by task 11610 on cpu 0:
 __tty_set_flow_change drivers/tty/tty.h:49 [inline]
 n_tty_check_throttle drivers/tty/n_tty.c:268 [inline]
 n_tty_receive_buf_common+0x4e39/0x4e70 drivers/tty/n_tty.c:1693
 n_tty_receive_buf+0x2b/0x40 drivers/tty/n_tty.c:1703
 tiocsti drivers/tty/tty_io.c:2310 [inline]
 tty_ioctl+0x969/0x1130 drivers/tty/tty_io.c:2719
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:860
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000001 -> 0x00000002

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11610 Comm: syz-executor.0 Not tainted 5.16.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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