syzbot

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BUG: KCSAN: data-race in n_tty_check_unthrottle / n_tty_receive_buf_common

write to 0xffff88813770a9e8 of 4 bytes by task 11088 on cpu 1:
 tty_set_flow_change drivers/tty/tty.h:54 [inline]
 n_tty_check_unthrottle+0xd8/0x1c0 drivers/tty/n_tty.c:288
 n_tty_read+0xe27/0x10b0 drivers/tty/n_tty.c:2176
 iterate_tty_read drivers/tty/tty_io.c:858 [inline]
 tty_read+0x19d/0x420 drivers/tty/tty_io.c:933
 call_read_iter include/linux/fs.h:2044 [inline]
 new_sync_read fs/read_write.c:401 [inline]
 vfs_read+0x5a5/0x6a0 fs/read_write.c:482
 ksys_read+0xe8/0x1a0 fs/read_write.c:620
 __do_sys_read fs/read_write.c:630 [inline]
 __se_sys_read fs/read_write.c:628 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:628
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

write to 0xffff88813770a9e8 of 4 bytes by task 11101 on cpu 0:
 n_tty_receive_buf_common+0x4c09/0x4c40
 n_tty_receive_buf+0x2b/0x40 drivers/tty/n_tty.c:1674
 tiocsti+0x14b/0x1a0 drivers/tty/tty_io.c:2293
 tty_ioctl+0x279/0x970 drivers/tty/tty_io.c:2692
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:856
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11101 Comm: syz-executor.0 Not tainted 5.18.0-rc6-syzkaller-00123-gf2dd007445b1-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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