mini-os: fix various memory leaks in blkfront

Coverity-ID: 1055814
Coverity-ID: 1055815
Signed-off-by: Matthew Daley <mattjd@gmail.com>
Acked-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

extras/mini-os/blkfront.c

@@ -250,7 +250,7 @@ error:
 
 void shutdown_blkfront(struct blkfront_dev *dev)
 {
-    char* err = NULL;
+    char* err = NULL, *err2;
     XenbusState state;
 
     char path[strlen(dev->backend) + strlen("/state") + 1];
@@ -295,12 +295,15 @@ void shutdown_blkfront(struct blkfront_dev *dev)
 
 close:
     if (err) free(err);
-    xenbus_unwatch_path_token(XBT_NIL, path, path);
+    err2 = xenbus_unwatch_path_token(XBT_NIL, path, path);
+    if (err2) free(err2);
 
     snprintf(nodename, sizeof(nodename), "%s/ring-ref", dev->nodename);
-    xenbus_rm(XBT_NIL, nodename);
+    err2 = xenbus_rm(XBT_NIL, nodename);
+    if (err2) free(err2);
     snprintf(nodename, sizeof(nodename), "%s/event-channel", dev->nodename);
-    xenbus_rm(XBT_NIL, nodename);
+    err2 = xenbus_rm(XBT_NIL, nodename);
+    if (err2) free(err2);
 
     if (!err)
         free_blkfront(dev);