virtio: Allow .get_vhost() without vhost_started

Historically, .get_vhost() was probably only called when
vdev->vhost_started is true.  However, we now decidedly want to call it
also when vhost_started is false, specifically so we can issue a reset
to the vhost back-end while device operation is stopped.

Some .get_vhost() implementations dereference some pointers (or return
offsets from them) that are probably guaranteed to be non-NULL when
vhost_started is true, but not necessarily otherwise.  This patch makes
all such implementations check all such pointers, returning NULL if any
is NULL.

Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-Id: <20240723163941.48775-2-hreitz@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 17 insertions, 2 deletions

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index ed33a32877..fb84d142ee 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -3896,8 +3896,23 @@ static bool dev_unplug_pending(void *opaque)
 static struct vhost_dev *virtio_net_get_vhost(VirtIODevice *vdev)
 {
     VirtIONet *n = VIRTIO_NET(vdev);
-    NetClientState *nc = qemu_get_queue(n->nic);
-    struct vhost_net *net = get_vhost_net(nc->peer);
+    NetClientState *nc;
+    struct vhost_net *net;
+
+    if (!n->nic) {
+        return NULL;
+    }
+
+    nc = qemu_get_queue(n->nic);
+    if (!nc) {
+        return NULL;
+    }
+
+    net = get_vhost_net(nc->peer);
+    if (!net) {
+        return NULL;
+    }
+
     return &net->dev;
 }