syzbot

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BUG: KCSAN: data-race in n_tty_check_unthrottle / n_tty_receive_buf_common

write to 0xffff888117e3f1dc of 4 bytes by task 4699 on cpu 0:
 tty_set_flow_change drivers/tty/tty.h:59 [inline]
 n_tty_check_unthrottle+0xd7/0x1c0 drivers/tty/n_tty.c:280
 n_tty_read+0xf05/0x11c0 drivers/tty/n_tty.c:2312
 iterate_tty_read drivers/tty/tty_io.c:856 [inline]
 tty_read+0x155/0x460 drivers/tty/tty_io.c:931
 do_iter_readv_writev+0x394/0x450
 vfs_readv+0x1df/0x660 fs/read_write.c:1011
 do_readv+0xf4/0x220 fs/read_write.c:1073
 __do_sys_readv fs/read_write.c:1158 [inline]
 __se_sys_readv fs/read_write.c:1155 [inline]
 __x64_sys_readv+0x45/0x50 fs/read_write.c:1155
 x64_sys_call+0x2c34/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:20
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888117e3f1dc of 4 bytes by task 1955 on cpu 1:
 n_tty_receive_buf_common+0xafa/0xbe0
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1785
 tty_ldisc_receive_buf+0x63/0x100 drivers/tty/tty_buffer.c:387
 tty_port_default_receive_buf+0x59/0x90 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:445 [inline]
 flush_to_ldisc+0x1ce/0x410 drivers/tty/tty_buffer.c:495
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3310
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3391
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 1955 Comm: kworker/u8:7 Not tainted 6.13.0-rc2-syzkaller-00333-ga0e3919a2df2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: events_unbound flush_to_ldisc
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