syzbot

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BUG: KCSAN: data-race in n_tty_receive_signal_char / n_tty_write

write to 0xffffc9000a547028 of 8 bytes by task 2422 on cpu 1:
 commit_echoes drivers/tty/n_tty.c:758 [inline]
 n_tty_receive_signal_char+0x2eb/0x3e0 drivers/tty/n_tty.c:1213
 n_tty_receive_buf_standard+0x6b6/0x2e20 drivers/tty/n_tty.c:1604
 __receive_buf drivers/tty/n_tty.c:1630 [inline]
 n_tty_receive_buf_common+0x7e5/0xbc0 drivers/tty/n_tty.c:1729
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1775
 tty_ldisc_receive_buf+0x60/0xe0 drivers/tty/tty_buffer.c:386
 tty_port_default_receive_buf+0x59/0x90 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:444 [inline]
 flush_to_ldisc+0x1ca/0x400 drivers/tty/tty_buffer.c:494
 process_one_work kernel/workqueue.c:2633 [inline]
 process_scheduled_works+0x5b8/0xa40 kernel/workqueue.c:2706
 worker_thread+0x525/0x730 kernel/workqueue.c:2787
 kthread+0x1d7/0x210 kernel/kthread.c:388
 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

read to 0xffffc9000a547028 of 8 bytes by task 13735 on cpu 0:
 process_echoes drivers/tty/n_tty.c:784 [inline]
 n_tty_write+0x161/0xb60 drivers/tty/n_tty.c:2365
 iterate_tty_write drivers/tty/tty_io.c:1021 [inline]
 file_tty_write+0x382/0x680 drivers/tty/tty_io.c:1096
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1117
 do_iter_readv_writev+0x2b0/0x330
 vfs_writev+0x2e9/0x860 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
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x0000000000000000 -> 0x000000000000003d

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 13735 Comm: syz-executor.1 Not tainted 6.8.0-rc4-syzkaller-00034-g8d3dea210042 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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