syzbot

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BUG: KCSAN: data-race in n_tty_receive_buf_common / n_tty_write

write to 0xffffc90001213020 of 8 bytes by task 29013 on cpu 0:
 process_echoes drivers/tty/n_tty.c:788 [inline]
 n_tty_write+0x1bc/0xb90 drivers/tty/n_tty.c:2375
 iterate_tty_write drivers/tty/tty_io.c:1021 [inline]
 file_tty_write+0x386/0x690 drivers/tty/tty_io.c:1096
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1117
 do_iter_readv_writev+0x339/0x3e0
 vfs_writev+0x2e4/0x890 fs/read_write.c:971
 do_writev+0xf8/0x220 fs/read_write.c:1018
 __do_sys_writev fs/read_write.c:1091 [inline]
 __se_sys_writev fs/read_write.c:1088 [inline]
 __x64_sys_writev+0x45/0x50 fs/read_write.c:1088
 x64_sys_call+0x1ee2/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:21
 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

read to 0xffffc90001213020 of 8 bytes by task 25384 on cpu 1:
 flush_echoes drivers/tty/n_tty.c:802 [inline]
 __receive_buf drivers/tty/n_tty.c:1642 [inline]
 n_tty_receive_buf_common+0x892/0xbe0 drivers/tty/n_tty.c:1739
 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:3231 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3312
 worker_thread+0x526/0x730 kernel/workqueue.c:3393
 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: 0x0000000000003f02 -> 0x0000000000003f04

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 25384 Comm: kworker/u8:34 Not tainted 6.10.0-rc4-syzkaller-00164-g66cc544fd75c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Workqueue: events_unbound flush_to_ldisc
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