[moderation] [serial?] KCSAN: data-race in n_tty_check_unthrottle / n_tty_receive_buf_common (8)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 55cb5f43689d Merge tag 'trace-v6.7-rc6' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1265014ee80000
kernel config: https://syzkaller.appspot.com/x/.config?x=989a728d0f884055
dashboard link: https://syzkaller.appspot.com/bug?extid=cfb147bc5c0c1506d040
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [gre...@linuxfoundation.org jiri...@kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/48e180dd5134/disk-55cb5f43.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8d5228b1803d/vmlinux-55cb5f43.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fc03913fb908/bzImage-55cb5f43.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cfb147...@syzkaller.appspotmail.com

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

write to 0xffff88813b7daddc of 4 bytes by task 24542 on cpu 1:
tty_set_flow_change drivers/tty/tty.h:59 [inline]
n_tty_check_throttle drivers/tty/n_tty.c:253 [inline]
n_tty_receive_buf_common+0xa6e/0xbc0 drivers/tty/n_tty.c:1748
n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1769
tiocsti+0x171/0x1d0 drivers/tty/tty_io.c:2295
tty_ioctl+0x415/0xbc0 drivers/tty/tty_io.c:2694
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xcf/0x140 fs/ioctl.c:857
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

write to 0xffff88813b7daddc of 4 bytes by task 24543 on cpu 0:
__tty_set_flow_change drivers/tty/tty.h:53 [inline]
n_tty_check_unthrottle+0x1a8/0x1c0 drivers/tty/n_tty.c:287
n_tty_read+0xf0a/0x11c0 drivers/tty/n_tty.c:2302
iterate_tty_read drivers/tty/tty_io.c:862 [inline]
tty_read+0x152/0x470 drivers/tty/tty_io.c:937
call_read_iter include/linux/fs.h:2014 [inline]
new_sync_read fs/read_write.c:389 [inline]
vfs_read+0x3c0/0x590 fs/read_write.c:470
ksys_read+0xeb/0x1a0 fs/read_write.c:613
__do_sys_read fs/read_write.c:623 [inline]
__se_sys_read fs/read_write.c:621 [inline]
__x64_sys_read+0x42/0x50 fs/read_write.c:621
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000002 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 24543 Comm: syz-executor.1 Not tainted 6.7.0-rc6-syzkaller-00022-g55cb5f43689d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.