linux-kernel - Re: [syzbot] INFO: task hung in add_early

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Date:   Wed, 8 Jun 2022 10:35:36 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     syzbot <syzbot+5b59d6d459306a556f54@...kaller.appspotmail.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        linux-crypto@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux@...inikbrodowski.net, mpm@...enic.com, mst <mst@...hat.com>,
        syzkaller-bugs@...glegroups.com,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, yuehaibing@...wei.com
Subject: Re: [syzbot] INFO: task hung in add_early_randomness (2)

On Wed, Jun 8, 2022 at 9:37 AM syzbot
<syzbot+5b59d6d459306a556f54@...kaller.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);