syzbot

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BUG: KCSAN: data-race in n_tty_check_unthrottle / n_tty_receive_buf_common

write to 0xffff88817d4481e8 of 4 bytes by task 5179 on cpu 1:
 tty_set_flow_change drivers/tty/tty.h:54 [inline]
 n_tty_check_unthrottle+0xd8/0x1c0 drivers/tty/n_tty.c:291
 n_tty_read+0xec6/0x1170 drivers/tty/n_tty.c:2278
 iterate_tty_read drivers/tty/tty_io.c:852 [inline]
 tty_read+0x17d/0x3e0 drivers/tty/tty_io.c:927
 call_read_iter include/linux/fs.h:2185 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x3a5/0x560 fs/read_write.c:470
 ksys_read+0xe8/0x1a0 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+0x3e/0x50 fs/read_write.c:621
 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+0x63/0xcd

write to 0xffff88817d4481e8 of 4 bytes by task 5181 on cpu 0:
 n_tty_receive_buf_common+0xbbc/0xbf0
 n_tty_receive_buf+0x2b/0x40 drivers/tty/n_tty.c:1740
 tiocsti+0x14b/0x1a0 drivers/tty/tty_io.c:2286
 tty_ioctl+0x244/0x940 drivers/tty/tty_io.c:2685
 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+0x63/0xcd

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5181 Comm: syz-executor.4 Not tainted 6.1.0-rc3-syzkaller-00332-g089d1c31224e-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
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