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

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Message-ID: <CAKFNMo=mAYHtfq+QP2v4v9YL7RxEMu-m0BdM5VCW65boHDt34g@mail.gmail.com>
Date: Sat, 28 Sep 2024 12:53:50 +0900
From: Ryusuke Konishi <konishi.ryusuke@...il.com>
To: syzbot <syzbot+8a192e8d090fa9a31135@...kaller.appspotmail.com>
Cc: Lizhi Xu <lizhi.xu@...driver.com>, linux-nilfs <linux-nilfs@...r.kernel.org>, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, 
	linux-serial@...r.kernel.org
Subject: Re: [syzbot] [serial?] INFO: task hung in vcs_open (8)

On Fri, Sep 27, 2024 at 2:36 AM syzbot
<syzbot+8a192e8d090fa9a31135@...kaller.appspotmail.com> wrote:
>
> 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
>

The problem caused by this reproducer seems to be an issue on the
nilfs side based on testing with Lizhi's patch (not all logs recorded
are like that), so I will add a nilfs tag:

#syz set subsystems: nilfs, serial

Ryusuke Konishi