linux-kernel - [syzbot] [serial?] INFO: task hung in vcs

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Message-ID: <66f59678.050a0220.46d20.0001.GAE@google.com>
Date: Thu, 26 Sep 2024 10:14:32 -0700
From: syzbot <syzbot+8a192e8d090fa9a31135@...kaller.appspotmail.com>
To: gregkh@...uxfoundation.org, jirislaby@...nel.org, 
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [serial?] INFO: task hung in vcs_open (8)

Hello,

syzbot found the following issue on:

HEAD commit:    88264981f208 Merge tag 'sched_ext-for-6.12' of git://git.k..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1187c19f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=74ffdb3b3fad1a43
dashboard link: https://syzkaller.appspot.com/bug?extid=8a192e8d090fa9a31135
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16aa3ca9980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1587c19f980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/87eaf0ad6d60/disk-88264981.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/30c01cf8bc82/vmlinux-88264981.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a1407424ea54/bzImage-88264981.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/a8a56914d1d8/mount_6.gz

Bisection is inconclusive: the issue happens on the oldest tested release.

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16154c80580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=15154c80580000
console output: https://syzkaller.appspot.com/x/log.txt?x=11154c80580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8a192e8d090fa9a31135@...kaller.appspotmail.com

INFO: task syz-executor199:5270 blocked for more than 147 seconds.
      Not tainted 6.11.0-syzkaller-08481-g88264981f208 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor199 state:D stack:27360 pid:5270  tgid:5255  ppid:5233   flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5315 [inline]
 __schedule+0x1843/0x4ae0 kernel/sched/core.c:6674
 __schedule_loop kernel/sched/core.c:6751 [inline]
 schedule+0x14b/0x320 kernel/sched/core.c:6766
 schedule_timeout+0xb0/0x310 kernel/time/timer.c:2591
 ___down_common kernel/locking/semaphore.c:225 [inline]
 __down_common+0x346/0x7f0 kernel/locking/semaphore.c:246
 down+0x84/0xc0 kernel/locking/semaphore.c:63
 console_lock+0x145/0x1b0 kernel/printk/printk.c:2808
 vcs_open+0x5d/0xd0 drivers/tty/vt/vc_screen.c:763
 chrdev_open+0x521/0x600 fs/char_dev.c:414
 do_dentry_open+0x978/0x1460 fs/open.c:958
 vfs_open+0x3e/0x330 fs/open.c:1088
 do_open fs/namei.c:3774 [inline]
 path_openat+0x2c84/0x3590 fs/namei.c:3933
 do_filp_open+0x235/0x490 fs/namei.c:3960


---
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 syzkaller@...glegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

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

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

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