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BUG: KCSAN: data-race in n_tty_read / pty_unix98_ioctl

write to 0xffff888137e12dd9 of 1 bytes by task 7750 on cpu 1:
 pty_unix98_ioctl+0x2a2/0x2e0 drivers/tty/pty.c:661
 tty_ioctl+0xa91/0x1130 drivers/tty/tty_io.c:2778
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:860
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888137e12dd9 of 1 bytes by task 7752 on cpu 0:
 n_tty_read+0x5ed/0x1070 drivers/tty/n_tty.c:2095
 iterate_tty_read drivers/tty/tty_io.c:858 [inline]
 tty_read+0x19c/0x430 drivers/tty/tty_io.c:933
 call_read_iter include/linux/fs.h:2068 [inline]
 new_sync_read fs/read_write.c:400 [inline]
 vfs_read+0x66c/0x750 fs/read_write.c:481
 ksys_read+0xd9/0x190 fs/read_write.c:619
 __do_sys_read fs/read_write.c:629 [inline]
 __se_sys_read fs/read_write.c:627 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:627
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7752 Comm: syz-executor.4 Not tainted 5.17.0-rc2-syzkaller-00353-g90c9e950c0de-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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