qcow2 v3 images require every snapshot table entry to have at least 16
bytes of extra data.  If they do not, let qemu-img check -r all fix it.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block/qcow2-snapshot.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 9e8c7c1f7f..e22c964b2a 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -502,6 +502,21 @@ int coroutine_fn qcow2_check_read_snapshot_table(BlockDriverState *bs,
         result->corruptions -= nb_clusters_reduced;
     }
 
+    /*
+     * All of v3 images' snapshot table entries need to have at least
+     * 16 bytes of extra data.
+     */
+    if (s->qcow_version >= 3) {
+        int i;
+        for (i = 0; i < s->nb_snapshots; i++) {
+            if (s->snapshots[i].extra_data_size < 16) {
+                result->corruptions++;
+                fprintf(stderr, "%s snapshot table entry %i is incomplete\n",
+                        fix & BDRV_FIX_ERRORS ? "Repairing" : "ERROR", i);
+            }
+        }
+    }
+
     return 0;
 }
 
-- 
2.21.0

On 7/30/19 12:25 PM, Max Reitz wrote:
> qcow2 v3 images require every snapshot table entry to have at least 16
> bytes of extra data.  If they do not, let qemu-img check -r all fix it.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/qcow2-snapshot.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
> index 9e8c7c1f7f..e22c964b2a 100644
> --- a/block/qcow2-snapshot.c
> +++ b/block/qcow2-snapshot.c
> @@ -502,6 +502,21 @@ int coroutine_fn qcow2_check_read_snapshot_table(BlockDriverState *bs,
>          result->corruptions -= nb_clusters_reduced;
>      }
>  
> +    /*
> +     * All of v3 images' snapshot table entries need to have at least
> +     * 16 bytes of extra data.
> +     */
> +    if (s->qcow_version >= 3) {
> +        int i;
> +        for (i = 0; i < s->nb_snapshots; i++) {
> +            if (s->snapshots[i].extra_data_size < 16) {

s/16/sizeof(extra)/ may be nicer here.

> +                result->corruptions++;
> +                fprintf(stderr, "%s snapshot table entry %i is incomplete\n",
> +                        fix & BDRV_FIX_ERRORS ? "Repairing" : "ERROR", i);
> +            }
> +        }
> +    }
> +
>      return 0;

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org