From: Kevin Wolf <kwolf@redhat.com>
Date: Wed, 26 Mar 2014 13:05:44 +0100
Subject: qcow2: Validate refcount table offset

The end of the refcount table must not exceed INT64_MAX so that integer
overflows are avoided.

Also check for misaligned refcount table. Such images are invalid and
probably the result of data corruption. Error out to avoid further
corruption.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 8c7de28305a514d7f879fdfc677ca11fbf60d2e9)

Conflicts:
	block/qcow2.c
	tests/qemu-iotests/080
	tests/qemu-iotests/080.out

diff --git a/block/qcow2.c b/block/qcow2.c
index fb1c9c1..3f0eab0 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -214,6 +214,32 @@ static void report_unsupported_feature(BlockDriverState *bs,
     }
 }
 
+static int validate_table_offset(BlockDriverState *bs, uint64_t offset,
+                                 uint64_t entries, size_t entry_len)
+{
+    BDRVQcowState *s = bs->opaque;
+    uint64_t size;
+
+    /* Use signed INT64_MAX as the maximum even for uint64_t header fields,
+     * because values will be passed to qemu functions taking int64_t. */
+    if (entries > INT64_MAX / entry_len) {
+        return -EINVAL;
+    }
+
+    size = entries * entry_len;
+
+    if (INT64_MAX - size < offset) {
+        return -EINVAL;
+    }
+
+    /* Tables must be cluster aligned */
+    if (offset & (s->cluster_size - 1)) {
+        return -EINVAL;
+    }
+
+    return 0;
+}
+
 static int qcow2_open(BlockDriverState *bs, int flags)
 {
     BDRVQcowState *s = bs->opaque;
@@ -365,6 +391,13 @@ static int qcow2_open(BlockDriverState *bs, int flags)
         goto fail;
     }
 
+    ret = validate_table_offset(bs, s->refcount_table_offset,
+                                s->refcount_table_size, sizeof(uint64_t));
+    if (ret < 0) {
+        report_unsupported(bs, "Invalid reference count table offset");
+        goto fail;
+    }
+
     s->snapshots_offset = header.snapshots_offset;
     s->nb_snapshots = header.nb_snapshots;
 
-- 
1.7.10.4