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BUG: KCSAN: data-race in n_tty_receive_char_special / n_tty_receive_char_special

write to 0xffffc90002ac1018 of 8 bytes by task 6421 on cpu 0:
 add_echo_byte drivers/tty/n_tty.c:845 [inline]
 echo_char_raw drivers/tty/n_tty.c:923 [inline]
 n_tty_receive_char_special+0x1a09/0x1bc0 drivers/tty/n_tty.c:1347
 n_tty_receive_buf_fast drivers/tty/n_tty.c:1610 [inline]
 __receive_buf drivers/tty/n_tty.c:1644 [inline]
 n_tty_receive_buf_common+0x17d6/0x1a40 drivers/tty/n_tty.c:1742
 n_tty_receive_buf+0x36/0x50 drivers/tty/n_tty.c:1771
 tiocsti drivers/tty/tty_io.c:2196 [inline]
 tty_ioctl+0xaf4/0xd80 drivers/tty/tty_io.c:2572
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x101/0x150 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x47/0x60 fs/ioctl.c:770
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffc90002ac1018 of 8 bytes by task 10862 on cpu 1:
 add_echo_byte drivers/tty/n_tty.c:845 [inline]
 echo_char_raw drivers/tty/n_tty.c:923 [inline]
 n_tty_receive_char_special+0x19f9/0x1bc0 drivers/tty/n_tty.c:1347
 n_tty_receive_buf_fast drivers/tty/n_tty.c:1610 [inline]
 __receive_buf drivers/tty/n_tty.c:1644 [inline]
 n_tty_receive_buf_common+0x17d6/0x1a40 drivers/tty/n_tty.c:1742
 n_tty_receive_buf2+0x39/0x50 drivers/tty/n_tty.c:1777
 tty_ldisc_receive_buf+0x69/0xe0 drivers/tty/tty_buffer.c:461
 paste_selection+0x170/0x2e0 drivers/tty/vt/selection.c:397
 tioclinux+0xf8/0x3d0 drivers/tty/vt/vt.c:3062
 vt_ioctl+0x15bb/0x1d90 drivers/tty/vt/vt_ioctl.c:372
 tty_ioctl+0x8de/0xd80 drivers/tty/tty_io.c:2656
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x101/0x150 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x47/0x60 fs/ioctl.c:770
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10862 Comm: syz-executor.3 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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