linux-kernel - Re: [syzbot] upstream boot error: INFO: task hung in hwrng

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Date:   Fri, 10 Jun 2022 10:36:37 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+6da75abeed821109137b@...kaller.appspotmail.com>
Cc:     herbert@...dor.apana.org.au, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux@...inikbrodowski.net,
        llvm@...ts.linux.dev, mpm@...enic.com,
        syzkaller-bugs@...glegroups.com, Jason Wang <jasowang@...hat.com>,
        Laurent Vivier <lvivier@...hat.com>
Subject: Re: [syzbot] upstream boot error: INFO: task hung in hwrng_register

On Sat, 4 Jun 2022 at 10:46, syzbot
<syzbot+6da75abeed821109137b@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    032dcf09e2bf Merge tag 'gpio-fixes-for-v5.19-rc1' of git:/..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14409a93f00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=99f457384a4fea79
> dashboard link: https://syzkaller.appspot.com/bug?extid=6da75abeed821109137b
> compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+6da75abeed821109137b@...kaller.appspotmail.com

+Jason, Laurent

This started appearing at the same time as 'task hung in
add_early_randomness" bug reports:
https://syzkaller.appspot.com/bug?id=256d08cc261a3c38832064a33df4c928b3cd0ef0
https://syzkaller.appspot.com/bug?id=be1d99e09e499aed3939dc678718371984104e5c
https://syzkaller.appspot.com/bug?id=1cd11df5d984c694e3e7fc9fe271389b2340bed0
https://syzkaller.appspot.com/bug?id=35496bafab4c3f81f0b0d6d72c69787300629740

Is this also fixed by "virtio-rng: make device ready before making
request" patch?




> INFO: task swapper/0:1 blocked for more than 143 seconds.
>       Not tainted 5.18.0-syzkaller-13760-g032dcf09e2bf #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:swapper/0       state:D stack:21080 pid:    1 ppid:     0 flags:0x00004000
> Call Trace:
>  <TASK>
>  context_switch kernel/sched/core.c:5116 [inline]
>  __schedule+0x957/0xec0 kernel/sched/core.c:6428
>  schedule+0xeb/0x1b0 kernel/sched/core.c:6500
>  schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6559
>  __mutex_lock_common+0xecf/0x26c0 kernel/locking/mutex.c:679
>  __mutex_lock kernel/locking/mutex.c:747 [inline]
>  mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
>  add_early_randomness drivers/char/hw_random/core.c:69 [inline]
>  hwrng_register+0x3bf/0x680 drivers/char/hw_random/core.c:599
>  virtrng_scan+0x3e/0x90 drivers/char/hw_random/virtio-rng.c:205
>  virtio_dev_probe+0xa03/0xba0 drivers/virtio/virtio.c:313
>  call_driver_probe+0x96/0x250
>  really_probe+0x220/0x940 drivers/base/dd.c:634
>  __driver_probe_device+0x1f4/0x3f0 drivers/base/dd.c:764
>  driver_probe_device+0x50/0x240 drivers/base/dd.c:794
>  __driver_attach+0x35f/0x5a0 drivers/base/dd.c:1163
>  bus_for_each_dev+0x188/0x1f0 drivers/base/bus.c:301
>  bus_add_driver+0x32f/0x600 drivers/base/bus.c:618
>  bus_add_driver+0x32f/0x600 drivers/base/bus.c:618
>  driver_register+0x2e9/0x3e0 drivers/base/driver.c:240
>  do_one_initcall+0xbd/0x2b0 init/main.c:1295
>  do_initcall_level+0x168/0x218 init/main.c:1368
>  do_initcalls+0x4b/0x8c init/main.c:1384
>  kernel_init_freeable+0x43a/0x5c3 init/main.c:1610
>  kernel_init+0x19/0x2b0 init/main.c:1499
>  ret_from_fork+0x1f/0x30
>  </TASK>
>
> Showing all locks held in the system:
> 2 locks held by swapper/0/1:
>  #0: ffff8881468d4170 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:835 [inline]
>  #0: ffff8881468d4170 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:1054 [inline]
>  #0: ffff8881468d4170 (&dev->mutex){....}-{3:3}, at: __driver_attach+0x353/0x5a0 drivers/base/dd.c:1162
>  #1: ffffffff8d24ccc8 (reading_mutex){+.+.}-{3:3}, at: add_early_randomness drivers/char/hw_random/core.c:69 [inline]
>  #1: ffffffff8d24ccc8 (reading_mutex){+.+.}-{3:3}, at: hwrng_register+0x3bf/0x680 drivers/char/hw_random/core.c:599
> 2 locks held by pr/ttyS0/16:
> 1 lock held by khungtaskd/29:
>  #0: ffffffff8cb1eee0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
> 2 locks held by kworker/u4:4/56:
>  #0: ffff888011c69138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x796/0xd10 kernel/workqueue.c:2262
>  #1: ffffc900013e7d00 ((work_completion)(&(&kfence_timer)->work)){+.+.}-{0:0}, at: process_one_work+0x7d0/0xd10 kernel/workqueue.c:2264
> 1 lock held by hwrng/755:
>  #0: ffffffff8d24ccc8 (reading_mutex){+.+.}-{3:3}, at: hwrng_fillfn+0xec/0x470 drivers/char/hw_random/core.c:503
>
> =============================================
>
>
>
> ---
> 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.
>
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