syzbot

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BUG: KCSAN: data-race in pty_stop / pty_unix98_ioctl

write to 0xffff8881199ed5d5 of 1 bytes by task 23416 on cpu 0:
 pty_set_pktmode drivers/tty/pty.c:-1 [inline]
 pty_unix98_ioctl+0x2c0/0x2e0 drivers/tty/pty.c:651
 tty_ioctl+0x7d8/0xb80 drivers/tty/tty_io.c:2792
 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+0x1816/0x3000 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881199ed5d5 of 1 bytes by task 12325 on cpu 1:
 pty_stop+0x3f/0xe0 drivers/tty/pty.c:339
 __stop_tty drivers/tty/tty_io.c:746 [inline]
 stop_tty+0x8d/0xe0 drivers/tty/tty_io.c:766
 n_tty_receive_char_flow_ctrl+0xec/0x1a0 drivers/tty/n_tty.c:1238
 n_tty_receive_char_special drivers/tty/n_tty.c:1343 [inline]
 n_tty_receive_buf_standard+0x4d2/0x2f10 drivers/tty/n_tty.c:1588
 __receive_buf drivers/tty/n_tty.c:1624 [inline]
 n_tty_receive_buf_common+0x805/0xbe0 drivers/tty/n_tty.c:1723
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1769
 tty_ldisc_receive_buf+0x66/0xf0 drivers/tty/tty_buffer.c:387
 tty_port_default_receive_buf+0x59/0x90 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:445 [inline]
 flush_to_ldisc+0x148/0x340 drivers/tty/tty_buffer.c:495
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3346
 worker_thread+0x582/0x770 kernel/workqueue.c:3427
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x122/0x1b0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 12325 Comm: kworker/u8:13 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: events_unbound flush_to_ldisc
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