vmdk: Fix error for JSON descriptor file names

If vmdk blindly tries to use path_combine() using bs->file->filename as
the base file name, this will result in a bad error message for JSON
file names when calling bdrv_open(). It is better to only try
bs->file->exact_filename; if that is empty, bs->file->filename will be
useless for path_combine() and an error should be emitted (containing
bs->file->filename because desc_file_path (which is
bs->file->exact_filename) is empty).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 1417615043-26174-2-git-send-email-mreitz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block.c

@@ -229,7 +229,7 @@ size_t bdrv_opt_mem_align(BlockDriverState *bs)
 }
 
 /* check if the path starts with "<protocol>:" */
-static int path_has_protocol(const char *path)
+int path_has_protocol(const char *path)
 {
     const char *p;
 

block/vmdk.c

@@ -833,6 +833,14 @@ static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
             goto next_line;
         }
 
+        if (!path_is_absolute(fname) && !path_has_protocol(fname) &&
+            !desc_file_path[0])
+        {
+            error_setg(errp, "Cannot use relative extent paths with VMDK "
+                       "descriptor file '%s'", bs->file->filename);
+            return -EINVAL;
+        }
+
         path_combine(extent_path, sizeof(extent_path),
                 desc_file_path, fname);
         extent_file = NULL;
@@ -909,7 +917,7 @@ static int vmdk_open_desc_file(BlockDriverState *bs, int flags, char *buf,
     }
     s->create_type = g_strdup(ct);
     s->desc_offset = 0;
-    ret = vmdk_parse_extents(buf, bs, bs->file->filename, errp);
+    ret = vmdk_parse_extents(buf, bs, bs->file->exact_filename, errp);
 exit:
     return ret;
 }

include/block/block.h

@@ -401,6 +401,7 @@ void bdrv_get_full_backing_filename(BlockDriverState *bs,
                                     char *dest, size_t sz);
 int bdrv_is_snapshot(BlockDriverState *bs);
 
+int path_has_protocol(const char *path);
 int path_is_absolute(const char *path);
 void path_combine(char *dest, int dest_size,
                   const char *base_path,