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BUG: KCSAN: data-race in n_tty_receive_buf_common / n_tty_write

write to 0xffffc90000861020 of 8 bytes by task 5873 on cpu 0:
 process_echoes drivers/tty/n_tty.c:798 [inline]
 n_tty_write+0x198/0xb10 drivers/tty/n_tty.c:2336
 do_tty_write drivers/tty/tty_io.c:1018 [inline]
 file_tty_write+0x3b8/0x620 drivers/tty/tty_io.c:1089
 tty_write+0x24/0x30 drivers/tty/tty_io.c:1110
 call_write_iter include/linux/fs.h:2186 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x468/0x760 fs/read_write.c:584
 ksys_write+0xe8/0x1a0 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+0x3e/0x50 fs/read_write.c:646
 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

read to 0xffffc90000861020 of 8 bytes by task 5874 on cpu 1:
 flush_echoes drivers/tty/n_tty.c:812 [inline]
 __receive_buf drivers/tty/n_tty.c:1615 [inline]
 n_tty_receive_buf_common+0x7cc/0xbe0 drivers/tty/n_tty.c:1711
 n_tty_receive_buf+0x2b/0x40 drivers/tty/n_tty.c:1740
 tiocsti+0x178/0x1d0 drivers/tty/tty_io.c:2290
 tty_ioctl+0x244/0x940 drivers/tty/tty_io.c:2689
 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: 0x0000000000000000 -> 0x0000000000000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5874 Comm: syz-executor.0 Not tainted 6.2.0-rc2-syzkaller-00010-g69b41ac87e4a-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
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