block: qapi - move string allocation from stack to the heap

Rather than declaring 'backing_filename2' on the stack in
bdrv_query_image_info(), dynamically allocate it on the heap.
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Signed-off-by: NJeff Cody <jcody@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/qapi.c

@@ -175,7 +175,6 @@ void bdrv_query_image_info(BlockDriverState *bs,
 {
     int64_t size;
     const char *backing_filename;
-    char backing_filename2[1024];
     BlockDriverInfo bdi;
     int ret;
     Error *err = NULL;
@@ -211,13 +210,14 @@ void bdrv_query_image_info(BlockDriverState *bs,
 
     backing_filename = bs->backing_file;
     if (backing_filename[0] != '\0') {
+        char *backing_filename2 = g_malloc0(1024);
         info->backing_filename = g_strdup(backing_filename);
         info->has_backing_filename = true;
-        bdrv_get_full_backing_filename(bs, backing_filename2,
-                                       sizeof(backing_filename2), &err);
+        bdrv_get_full_backing_filename(bs, backing_filename2, 1024, &err);
         if (err) {
             error_propagate(errp, err);
             qapi_free_ImageInfo(info);
+            g_free(backing_filename2);
             return;
         }
 
@@ -231,6 +231,7 @@ void bdrv_query_image_info(BlockDriverState *bs,
             info->backing_filename_format = g_strdup(bs->backing_format);
             info->has_backing_filename_format = true;
         }
+        g_free(backing_filename2);
     }
 
     ret = bdrv_query_snapshot_info_list(bs, &info->snapshots, &err);