qcow2: Increase maximum cluster size to 2 MB

This patch increases the maximum qcow2 cluster size to 2 MB. Starting with 128k
clusters, L2 tables span 2 GB or more of virtual disk space, causing 32 bit
truncation and wraparound of signed integers. Therefore some variables need to
use a larger data type.

While being at reviewing data types, change some integers that are used for
array indices to unsigned. In some places they were checked against some upper
limit but not for negative values. This could avoid potential segfaults with
corrupted qcow2 images.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 54e505c..e444e53 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -264,7 +264,7 @@ static int count_contiguous_clusters(uint64_t nb_clusters, int cluster_size,
         return 0;
 
     for (i = start; i < start + nb_clusters; i++)
-        if (offset + i * cluster_size != (be64_to_cpu(l2_table[i]) & ~mask))
+        if (offset + (uint64_t) i * cluster_size != (be64_to_cpu(l2_table[i]) & ~mask))
             break;
 
 	return (i - start);
@@ -395,10 +395,11 @@ uint64_t qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
     int *num)
 {
     BDRVQcowState *s = bs->opaque;
-    int l1_index, l2_index;
+    unsigned int l1_index, l2_index;
     uint64_t l2_offset, *l2_table, cluster_offset;
     int l1_bits, c;
-    int index_in_cluster, nb_available, nb_needed, nb_clusters;
+    unsigned int index_in_cluster, nb_clusters;
+    uint64_t nb_available, nb_needed;
 
     index_in_cluster = (offset >> 9) & (s->cluster_sectors - 1);
     nb_needed = *num + index_in_cluster;
@@ -409,7 +410,7 @@ uint64_t qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
      * the end of the l1 entry
      */
 
-    nb_available = (1 << l1_bits) - (offset & ((1 << l1_bits) - 1));
+    nb_available = (1ULL << l1_bits) - (offset & ((1ULL << l1_bits) - 1));
 
     /* compute the number of available sectors */
 
@@ -483,8 +484,9 @@ static int get_cluster_table(BlockDriverState *bs, uint64_t offset,
                              int *new_l2_index)
 {
     BDRVQcowState *s = bs->opaque;
-    int l1_index, l2_index, ret;
+    unsigned int l1_index, l2_index;
     uint64_t l2_offset, *l2_table;
+    int ret;
 
     /* seek the the l2 offset in the l1 table */
 
@@ -683,7 +685,7 @@ uint64_t qcow2_alloc_cluster_offset(BlockDriverState *bs,
     BDRVQcowState *s = bs->opaque;
     int l2_index, ret;
     uint64_t l2_offset, *l2_table, cluster_offset;
-    int nb_clusters, i = 0;
+    unsigned int nb_clusters, i = 0;
     QCowL2Meta *old_alloc;
 
     ret = get_cluster_table(bs, offset, &l2_table, &l2_offset, &l2_index);