The payload size returned by command VIRTIO_SND_R_PCM_INFO is
wrong. The code in process_cmd() assumes that all commands
return only a virtio_snd_hdr payload, but some commands like
VIRTIO_SND_R_PCM_INFO may return an additional payload.

Add a zero initialized payload_size variable to struct
virtio_snd_ctrl_command to allow for additional payloads.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
---
 hw/audio/virtio-snd.c         | 7 +++++--
 include/hw/audio/virtio-snd.h | 1 +
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/hw/audio/virtio-snd.c b/hw/audio/virtio-snd.c
index ea2aeaef14..e604d8f30c 100644
--- a/hw/audio/virtio-snd.c
+++ b/hw/audio/virtio-snd.c
@@ -243,12 +243,13 @@ static void virtio_snd_handle_pcm_info(VirtIOSound *s,
         memset(&pcm_info[i].padding, 0, 5);
     }
 
+    cmd->payload_size = sizeof(virtio_snd_pcm_info) * count;
     cmd->resp.code = cpu_to_le32(VIRTIO_SND_S_OK);
     iov_from_buf(cmd->elem->in_sg,
                  cmd->elem->in_num,
                  sizeof(virtio_snd_hdr),
                  pcm_info,
-                 sizeof(virtio_snd_pcm_info) * count);
+                 cmd->payload_size);
 }
 
 /*
@@ -749,7 +750,8 @@ process_cmd(VirtIOSound *s, virtio_snd_ctrl_command *cmd)
                  0,
                  &cmd->resp,
                  sizeof(virtio_snd_hdr));
-    virtqueue_push(cmd->vq, cmd->elem, sizeof(virtio_snd_hdr));
+    virtqueue_push(cmd->vq, cmd->elem,
+                   sizeof(virtio_snd_hdr) + cmd->payload_size);
     virtio_notify(VIRTIO_DEVICE(s), cmd->vq);
 }
 
@@ -808,6 +810,7 @@ static void virtio_snd_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
         cmd->elem = elem;
         cmd->vq = vq;
         cmd->resp.code = cpu_to_le32(VIRTIO_SND_S_OK);
+        /* implicit cmd->payload_size = 0; */
         QTAILQ_INSERT_TAIL(&s->cmdq, cmd, next);
         elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
     }
diff --git a/include/hw/audio/virtio-snd.h b/include/hw/audio/virtio-snd.h
index c3767f442b..3d79181364 100644
--- a/include/hw/audio/virtio-snd.h
+++ b/include/hw/audio/virtio-snd.h
@@ -230,6 +230,7 @@ struct virtio_snd_ctrl_command {
     VirtQueue *vq;
     virtio_snd_hdr ctrl;
     virtio_snd_hdr resp;
+    size_t payload_size;
     QTAILQ_ENTRY(virtio_snd_ctrl_command) next;
 };
 #endif
-- 
2.35.3