xen-netback: respect gnttab_map_refs()'s return value

Commit 3194a1746e8a ("xen-netback: don't "handle" error by BUG()")
dropped respective a BUG_ON() without noticing that with this the
variable's value wouldn't be consumed anymore. With gnttab_set_map_op()
setting all status fields to a non-zero value, in case of an error no
slot should have a status of GNTST_okay (zero).

This is part of XSA-367.

Cc: <stable@vger.kernel.org>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/d933f495-619a-0086-5fb4-1ec3cf81a8fc@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index e5c73f8..6afb5ca 100644 (file)
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1343,11 +1343,21 @@ int xenvif_tx_action(struct xenvif_queue *queue, int budget)
                return 0;
 
        gnttab_batch_copy(queue->tx_copy_ops, nr_cops);
-       if (nr_mops != 0)
+       if (nr_mops != 0) {
                ret = gnttab_map_refs(queue->tx_map_ops,
                                      NULL,
                                      queue->pages_to_map,
                                      nr_mops);
+               if (ret) {
+                       unsigned int i;
+
+                       netdev_err(queue->vif->dev, "Map fail: nr %u ret %d\n",
+                                  nr_mops, ret);
+                       for (i = 0; i < nr_mops; ++i)
+                               WARN_ON_ONCE(queue->tx_map_ops[i].status ==
+                                            GNTST_okay);
+               }
+       }
 
        work_done = xenvif_tx_submit(queue);