[UNIKRAFT PATCH 3/5] plat/drivers/virtio: Add error check for return value

[Vlad-Andrei Badoiu <vlad_andrei.badoiu@xxxxxx>]

If virtio_config_get return an error then tag_len does
not get initialized and the next calloc is ran with an
unitialized length.
---
 plat/drivers/virtio/virtio_9p.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/plat/drivers/virtio/virtio_9p.c b/plat/drivers/virtio/virtio_9p.c
index fe0d69ab..045ce42f 100644
--- a/plat/drivers/virtio/virtio_9p.c
+++ b/plat/drivers/virtio/virtio_9p.c
@@ -345,9 +345,13 @@ static int virtio_9p_feature_negotiate(struct 
virtio_9p_device *d)
                goto out;
        }
 
-       virtio_config_get(d->vdev,
+       if (virtio_config_get(d->vdev,
                          __offsetof(struct virtio_9p_config, tag_len),
-                         &tag_len, 1, sizeof(tag_len));
+                         &tag_len, 1, sizeof(tag_len)))
+       {
+               rc = -EAGAIN;
+               goto out;
+       }
 
        d->tag = uk_calloc(a, tag_len + 1, sizeof(*d->tag));
        if (!d->tag) {
-- 
2.27.0