Re: [syzbot] INFO: task hung in add_early_randomness (2)

From: Jason Wang <jasowang@redhat.com>
To: syzbot <syzbot+5b59d6d459306a556f54@syzkaller.appspotmail.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>,
	linux-crypto@vger.kernel.org,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux@dominikbrodowski.net, mpm@selenic.com, mst <mst@redhat.com>,
	syzkaller-bugs@googlegroups.com,
	Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
	yuehaibing@huawei.com
Subject: Re: [syzbot] INFO: task hung in add_early_randomness (2)
Date: Wed, 8 Jun 2022 10:35:36 +0800	[thread overview]
Message-ID: <CACGkMEt_e59wRotUo9D1UqubAhe+txy0GF=r1BYBVdND8-uKbA@mail.gmail.com> (raw)
In-Reply-To: <000000000000a09fc105e0e5bedb@google.com>

On Wed, Jun 8, 2022 at 9:37 AM syzbot
<syzbot+5b59d6d459306a556f54@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> INFO: task hung in add_early_randomness
>

Ok, looking at virtio-rng.c, probe_common() tries to kick the
virtqueue before DRIVER_OK which is kind of violates the spec.

Please test the following patch:

#syz test
git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git linux-next

diff --git a/drivers/char/hw_random/virtio-rng.c
b/drivers/char/hw_random/virtio-rng.c
index e856df7e285c..a6f3a8a2aca6 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -159,6 +159,8 @@ static int probe_common(struct virtio_device *vdev)
                goto err_find;
        }

+       virtio_device_ready(vdev);
+
        /* we always have a pending entropy request */
        request_entropy(vi);

