diff --git a/block.c b/block.c
index a12b1d3..083f4ae 100644
--- a/block.c
+++ b/block.c
@@ -218,19 +218,13 @@ char *bdrv_get_full_backing_filename_from_filename(const char *backed,
     }
 }
 
-void bdrv_get_full_backing_filename(BlockDriverState *bs, char *dest, size_t sz,
-                                    Error **errp)
+char *bdrv_get_full_backing_filename(BlockDriverState *bs, Error **errp)
 {
     char *backed = bs->exact_filename[0] ? bs->exact_filename : bs->filename;
-    char *full_name;
 
-    full_name = bdrv_get_full_backing_filename_from_filename(backed,
-                                                             bs->backing_file,
-                                                             errp);
-    if (full_name) {
-        pstrcpy(dest, sz, full_name);
-        g_free(full_name);
-    }
+    return bdrv_get_full_backing_filename_from_filename(backed,
+                                                        bs->backing_file,
+                                                        errp);
 }
 
 void bdrv_register(BlockDriver *bdrv)
@@ -1289,7 +1283,7 @@ out:
 int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
                            const char *bdref_key, Error **errp)
 {
-    char *backing_filename = g_malloc0(PATH_MAX);
+    char *backing_filename = NULL;
     char *bdref_key_dot;
     const char *reference = NULL;
     int ret = 0;
@@ -1317,13 +1311,12 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
     reference = qdict_get_try_str(parent_options, bdref_key);
     if (reference || qdict_haskey(options, "file.filename")) {
         bs->backing_overridden = true;
-        backing_filename[0] = '\0';
+        backing_filename = NULL;
     } else if (bs->backing_file[0] == '\0' && qdict_size(options) == 0) {
         QDECREF(options);
         goto free_exit;
     } else {
-        bdrv_get_full_backing_filename(bs, backing_filename, PATH_MAX,
-                                       &local_err);
+        backing_filename = bdrv_get_full_backing_filename(bs, &local_err);
         if (local_err) {
             ret = -EINVAL;
             error_propagate(errp, local_err);
@@ -1344,8 +1337,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
     }
 
     backing_hd = NULL;
-    ret = bdrv_open_inherit(&backing_hd,
-                            *backing_filename ? backing_filename : NULL,
+    ret = bdrv_open_inherit(&backing_hd, backing_filename,
                             reference, options, 0, bs, &child_backing,
                             errp);
     if (ret < 0) {
diff --git a/block/qapi.c b/block/qapi.c
index c5f6ba6..a0fb7fb 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -265,18 +265,10 @@ void bdrv_query_image_info(BlockDriverState *bs,
 
     backing_filename = bs->backing_file;
     if (backing_filename[0] != '\0') {
-        char *backing_filename2 = g_malloc0(PATH_MAX);
+        char *backing_filename2;
         info->backing_filename = g_strdup(backing_filename);
         info->has_backing_filename = true;
-        bdrv_get_full_backing_filename(bs, backing_filename2, PATH_MAX, &err);
-        if (err) {
-            /* Can't reconstruct the full backing filename, so we must omit
-             * this field and apply a Best Effort to this query. */
-            g_free(backing_filename2);
-            backing_filename2 = NULL;
-            error_free(err);
-            err = NULL;
-        }
+        backing_filename2 = bdrv_get_full_backing_filename(bs, NULL);
 
         /* Always report the full_backing_filename if present, even if it's the
          * same as backing_filename. That they are same is useful info. */
diff --git a/include/block/block.h b/include/block/block.h
index c6c00dd..83f9f31 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -433,8 +433,7 @@ void bdrv_round_to_clusters(BlockDriverState *bs,
 const char *bdrv_get_encrypted_filename(BlockDriverState *bs);
 void bdrv_get_backing_filename(BlockDriverState *bs,
                                char *filename, int filename_size);
-void bdrv_get_full_backing_filename(BlockDriverState *bs,
-                                    char *dest, size_t sz, Error **errp);
+char *bdrv_get_full_backing_filename(BlockDriverState *bs, Error **errp);
 char *bdrv_get_full_backing_filename_from_filename(const char *backed,
                                                    const char *backing,
                                                    Error **errp);
