syzbot

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BUG: KCSAN: data-race in n_tty_write / tty_set_termios

read-write to 0xffff88814e300d14 of 4 bytes by task 18701 on cpu 1:
 unset_locked_termios drivers/tty/tty_ioctl.c:217 [inline]
 tty_set_termios+0x1a2/0x8b0 drivers/tty/tty_ioctl.c:340
 set_termios+0x365/0x4e0 drivers/tty/tty_ioctl.c:520
 tty_mode_ioctl+0x391/0x5d0
 n_tty_ioctl_helper+0x8d/0x240 drivers/tty/tty_ioctl.c:986
 n_tty_ioctl+0xfd/0x200 drivers/tty/n_tty.c:2521
 tty_ioctl+0x87a/0xbe0 drivers/tty/tty_io.c:2812
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:892
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
 x64_sys_call+0x1690/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88814e300d14 of 4 bytes by task 18700 on cpu 0:
 n_tty_write+0xa0/0xb80 drivers/tty/n_tty.c:2366
 iterate_tty_write drivers/tty/tty_io.c:1015 [inline]
 file_tty_write+0x37a/0x680 drivers/tty/tty_io.c:1090
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1111
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0x77f/0x920 fs/read_write.c:679
 ksys_write+0xe8/0x1b0 fs/read_write.c:731
 __do_sys_write fs/read_write.c:742 [inline]
 __se_sys_write fs/read_write.c:739 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:739
 x64_sys_call+0x287e/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00008a3b -> 0x00000006

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 18700 Comm: syz.9.20585 Not tainted 6.13.0-rc2-syzkaller-00192-g243f750a2df0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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