syzbot

==================================================================
BUG: KCSAN: data-race in n_tty_check_unthrottle / n_tty_receive_buf_common

write to 0xffff8881165861dc of 4 bytes by task 25293 on cpu 0:
 tty_set_flow_change drivers/tty/tty.h:59 [inline]
 n_tty_check_unthrottle+0xd7/0x1c0 drivers/tty/n_tty.c:280
 n_tty_read+0xf0b/0x11d0 drivers/tty/n_tty.c:2302
 iterate_tty_read drivers/tty/tty_io.c:862 [inline]
 tty_read+0x15b/0x480 drivers/tty/tty_io.c:937
 do_iter_readv_writev+0x339/0x3e0
 vfs_readv+0x1e5/0x650 fs/read_write.c:932
 do_readv+0xf8/0x220 fs/read_write.c:994
 __do_sys_readv fs/read_write.c:1085 [inline]
 __se_sys_readv fs/read_write.c:1082 [inline]
 __x64_sys_readv+0x45/0x50 fs/read_write.c:1082
 x64_sys_call+0x2bbd/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:20
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff8881165861dc of 4 bytes by task 25295 on cpu 1:
 n_tty_receive_buf_common+0xae5/0xbd0
 n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1769
 tiocsti+0x166/0x1d0 drivers/tty/tty_io.c:2299
 tty_ioctl+0x415/0xbe0 drivers/tty/tty_io.c:2717
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:904 [inline]
 __se_sys_ioctl+0xd3/0x150 fs/ioctl.c:890
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:890
 x64_sys_call+0x155d/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 25295 Comm: syz-executor.4 Tainted: G        W          6.9.0-rc7-syzkaller-00056-g45db3ab70092 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
==================================================================