usb-mtp: return incomplete transfer on a lstat failure

MTP writes objects in small chunks and at the end gets the
real file size to update the object metadata. If this fails for
any reason, return an INCOMPLETE_TRANSFER to the initiator

Spotted by Coverity: CID 1398651

Signed-off-by: Bandan Das <bsd@redhat.com>
Message-id: 20190306210409.14842-2-bsd@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/usb/dev-mtp.c

@@ -1591,14 +1591,18 @@ done:
         return ret;
 }
 
-static void usb_mtp_update_object(MTPObject *parent, char *name)
+static int usb_mtp_update_object(MTPObject *parent, char *name)
 {
+    int ret = -1;
+
     MTPObject *o =
         usb_mtp_object_lookup_name(parent, name, strlen(name));
 
     if (o) {
-        lstat(o->path, &o->stat);
+        ret = lstat(o->path, &o->stat);
     }
+
+    return ret;
 }
 
 static void usb_mtp_write_data(MTPState *s)
@@ -1655,13 +1659,18 @@ static void usb_mtp_write_data(MTPState *s)
         if (d->write_status != WRITE_END) {
             return;
         } else {
-            /* Only for < 4G file sizes */
-            if (s->dataset.size != 0xFFFFFFFF && d->offset != s->dataset.size) {
+            /*
+             * Return an incomplete transfer if file size doesn't match
+             * for < 4G file or if lstat fails which will result in an incorrect
+             * file size
+             */
+            if ((s->dataset.size != 0xFFFFFFFF &&
+                 d->offset != s->dataset.size) ||
+                usb_mtp_update_object(parent, s->dataset.filename)) {
                 usb_mtp_queue_result(s, RES_INCOMPLETE_TRANSFER, d->trans,
                                      0, 0, 0, 0);
                 goto done;
             }
-            usb_mtp_update_object(parent, s->dataset.filename);
         }
     }