syzbot

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BUG: KCSAN: data-race in n_tty_write / tty_set_termios

read-write to 0xffff888137387514 of 4 bytes by task 882 on cpu 0:
 unset_locked_termios drivers/tty/tty_ioctl.c:234 [inline]
 tty_set_termios+0x1a2/0x8a0 drivers/tty/tty_ioctl.c:358
 set_termios+0x241/0x270 drivers/tty/tty_ioctl.c:517
 tty_mode_ioctl+0x3e1/0x580
 n_tty_ioctl_helper+0x8d/0x240 drivers/tty/tty_ioctl.c:980
 n_tty_ioctl+0xfd/0x200 drivers/tty/n_tty.c:2483
 tty_ioctl+0x86f/0xbc0 drivers/tty/tty_io.c:2786
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:856
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:856
 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 0xffff888137387514 of 4 bytes by task 867 on cpu 1:
 n_tty_write+0xa0/0xa80 drivers/tty/n_tty.c:2327
 do_tty_write drivers/tty/tty_io.c:1018 [inline]
 file_tty_write+0x3a0/0x600 drivers/tty/tty_io.c:1089
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1110
 do_iter_write+0x418/0x700 fs/read_write.c:861
 vfs_writev+0x1a2/0x310 fs/read_write.c:934
 do_writev+0xf8/0x220 fs/read_write.c:977
 __do_sys_writev fs/read_write.c:1050 [inline]
 __se_sys_writev fs/read_write.c:1047 [inline]
 __x64_sys_writev+0x45/0x50 fs/read_write.c:1047
 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: 0x00000003 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 867 Comm: syz-executor.3 Not tainted 6.3.0-rc7-syzkaller-00060-g789b4a41c247 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
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