syzbot

==================================================================
BUG: KCSAN: data-race in n_tty_write / tty_set_termios

write to 0xffff88811ba78d08 of 44 bytes by task 5155 on cpu 1:
 tty_set_termios+0xc0/0x8c0 drivers/tty/tty_ioctl.c:335
 set_termios+0x35b/0x4d0 drivers/tty/tty_ioctl.c:516
 tty_mode_ioctl+0x379/0x5c0 drivers/tty/tty_ioctl.c:-1
 n_tty_ioctl_helper+0x91/0x210 drivers/tty/tty_ioctl.c:982
 n_tty_ioctl+0x101/0x230 drivers/tty/n_tty.c:2496
 tty_ioctl+0x83f/0xb80 drivers/tty/tty_io.c:2801
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x14b0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811ba78d14 of 4 bytes by task 5152 on cpu 0:
 n_tty_write+0x9c/0xbf0 drivers/tty/n_tty.c:2343
 iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
 file_tty_write+0x378/0x690 drivers/tty/tty_io.c:1081
 tty_write+0x25/0x30 drivers/tty/tty_io.c:1102
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x52a/0x960 fs/read_write.c:686
 ksys_write+0xda/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x2847/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00008a3b -> 0x00000009

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 5152 Comm: syz.0.719 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================