hostmem-file: fixed the memory leak while get pmem path.

object_get_canonical_path_component() returns a string which
must be freed using g_free().

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
Message-Id: <7328fb16c394eaf5d65437d11c2a9343647b6d3d.1535471899.git.yi.z.zhang@linux.intel.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

backends/hostmem-file.c

@@ -145,20 +145,26 @@ static void file_memory_backend_set_pmem(Object *o, bool value, Error **errp)
     HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
 
     if (host_memory_backend_mr_inited(backend)) {
+        char *path = object_get_canonical_path_component(o);
+
         error_setg(errp, "cannot change property 'pmem' of %s '%s'",
                    object_get_typename(o),
-                   object_get_canonical_path_component(o));
+                   path);
+        g_free(path);
         return;
     }
 
 #ifndef CONFIG_LIBPMEM
     if (value) {
         Error *local_err = NULL;
+        char *path = object_get_canonical_path_component(o);
+
         error_setg(&local_err,
                    "Lack of libpmem support while setting the 'pmem=on'"
                    " of %s '%s'. We can't ensure data persistence.",
                    object_get_typename(o),
-                   object_get_canonical_path_component(o));
+                   path);
+        g_free(path);
         error_propagate(errp, local_err);
         return;
     }