qcow2: Fix access after end of array

Submitted by Kevin Wolf on Feb. 16, 2010, 2:54 p.m.

Details

Message ID 1266332089-14381-1-git-send-email-kwolf@redhat.com
State New
Headers show

Commit Message

Kevin Wolf Feb. 16, 2010, 2:54 p.m.
If a write requests crosses a L2 table boundary and all clusters until the
end of the L2 table are usable for the request, we must not look at the next
L2 entry because we already have arrived at the end of the array.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow2-cluster.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

Comments

Anthony Liguori Feb. 19, 2010, 10:01 p.m.
On 02/16/2010 08:54 AM, Kevin Wolf wrote:
> If a write requests crosses a L2 table boundary and all clusters until the
> end of the L2 table are usable for the request, we must not look at the next
> L2 entry because we already have arrived at the end of the array.
>
> Signed-off-by: Kevin Wolf<kwolf@redhat.com>
>    

Applied.  Thanks.

Regards,

Anthony Liguori
> ---
>   block/qcow2-cluster.c |    8 ++++++--
>   1 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index 3501a94..b13b693 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c
> @@ -750,12 +750,15 @@ int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
>       while (i<  nb_clusters) {
>           i += count_contiguous_clusters(nb_clusters - i, s->cluster_size,
>                   &l2_table[l2_index], i, 0);
> -
> -        if(be64_to_cpu(l2_table[l2_index + i]))
> +        if ((i>= nb_clusters) || be64_to_cpu(l2_table[l2_index + i])) {
>               break;
> +        }
>
>           i += count_contiguous_free_clusters(nb_clusters - i,
>                   &l2_table[l2_index + i]);
> +        if (i>= nb_clusters) {
> +            break;
> +        }
>
>           cluster_offset = be64_to_cpu(l2_table[l2_index + i]);
>
> @@ -763,6 +766,7 @@ int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
>                   (cluster_offset&  QCOW_OFLAG_COMPRESSED))
>               break;
>       }
> +    assert(i<= nb_clusters);
>       nb_clusters = i;
>
>       /*
>

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diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 3501a94..b13b693 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -750,12 +750,15 @@  int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
     while (i < nb_clusters) {
         i += count_contiguous_clusters(nb_clusters - i, s->cluster_size,
                 &l2_table[l2_index], i, 0);
-
-        if(be64_to_cpu(l2_table[l2_index + i]))
+        if ((i >= nb_clusters) || be64_to_cpu(l2_table[l2_index + i])) {
             break;
+        }
 
         i += count_contiguous_free_clusters(nb_clusters - i,
                 &l2_table[l2_index + i]);
+        if (i >= nb_clusters) {
+            break;
+        }
 
         cluster_offset = be64_to_cpu(l2_table[l2_index + i]);
 
@@ -763,6 +766,7 @@  int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
                 (cluster_offset & QCOW_OFLAG_COMPRESSED))
             break;
     }
+    assert(i <= nb_clusters);
     nb_clusters = i;
 
     /*