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BUG: KCSAN: data-race in n_tty_receive_buf_common / n_tty_write

write to 0xffffc9000f745020 of 8 bytes by task 13243 on cpu 0:
 process_echoes drivers/tty/n_tty.c:793 [inline]
 n_tty_write+0x1b9/0xb60 drivers/tty/n_tty.c:2370
 iterate_tty_write drivers/tty/tty_io.c:1017 [inline]
 file_tty_write+0x398/0x6b0 drivers/tty/tty_io.c:1088
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1109
 call_write_iter include/linux/fs.h:1985 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x4ab/0x7d0 fs/read_write.c:584
 ksys_write+0xeb/0x1a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:646
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffffc9000f745020 of 8 bytes by task 13242 on cpu 1:
 flush_echoes drivers/tty/n_tty.c:807 [inline]
 __receive_buf drivers/tty/n_tty.c:1637 [inline]
 n_tty_receive_buf_common+0x87d/0xbc0 drivers/tty/n_tty.c:1734
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1780
 tty_ldisc_receive_buf+0x60/0xe0 drivers/tty/tty_buffer.c:387
 paste_selection+0x1dd/0x2e0 drivers/tty/vt/selection.c:409
 tioclinux+0x2a5/0x450 drivers/tty/vt/vt.c:3161
 vt_ioctl+0x84e/0x1830 drivers/tty/vt/vt_ioctl.c:762
 tty_ioctl+0x816/0xbc0 drivers/tty/tty_io.c:2776
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xcf/0x140 fs/ioctl.c:857
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000000000 -> 0x0000000000000050

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 13242 Comm: syz-executor.1 Tainted: G        W          6.6.0-rc1-syzkaller-00196-g57d88e8a5974 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
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