syzbot

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BUG: KCSAN: data-race in n_tty_check_unthrottle / n_tty_receive_buf_common

write to 0xffff8881179975dc of 4 bytes by task 5221 on cpu 0:
 tty_set_flow_change drivers/tty/tty.h:59 [inline]
 n_tty_check_unthrottle+0xdd/0x1d0 drivers/tty/n_tty.c:280
 n_tty_read+0xab3/0xd30 drivers/tty/n_tty.c:2312
 iterate_tty_read drivers/tty/tty_io.c:856 [inline]
 tty_read+0x15a/0x480 drivers/tty/tty_io.c:931
 new_sync_read fs/read_write.c:489 [inline]
 vfs_read+0x5e6/0x710 fs/read_write.c:570
 ksys_read+0xeb/0x1b0 fs/read_write.c:713
 __do_sys_read fs/read_write.c:722 [inline]
 __se_sys_read fs/read_write.c:720 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:720
 x64_sys_call+0x2a3b/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff8881179975dc of 4 bytes by task 5225 on cpu 1:
 n_tty_receive_buf_common+0xaf4/0xbe0 drivers/tty/n_tty.c:-1
 n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1779
 tiocsti+0x16b/0x1d0 drivers/tty/tty_io.c:2299
 tty_ioctl+0x409/0xbe0 drivers/tty/tty_io.c:2716
 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+0x168d/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 5225 Comm: syz.3.655 Not tainted 6.14.0-syzkaller-12508-g92b71befc349 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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