xen/netfront: tolerate frags with no data

[ Upstream commit d81c5054a5d1d4999c7cdead7636b6cd4af83d36 ]

At least old Xen net backends seem to send frags with no real data
sometimes. In case such a fragment happens to occur with the frag limit
already reached the frontend will BUG currently even if this situation
is easily recoverable.

Modify the BUG_ON() condition accordingly.

Tested-by: Dietmar Hahn <dietmar.hahn@ts.fujitsu.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 0a4bd73..6f55ab4 100644 (file)
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -889,7 +889,7 @@ static RING_IDX xennet_fill_frags(struct netfront_queue *queue,
                if (skb_shinfo(skb)->nr_frags == MAX_SKB_FRAGS) {
                        unsigned int pull_to = NETFRONT_SKB_CB(skb)->pull_to;
 
-                       BUG_ON(pull_to <= skb_headlen(skb));
+                       BUG_ON(pull_to < skb_headlen(skb));
                        __pskb_pull_tail(skb, pull_to - skb_headlen(skb));
                }
                if (unlikely(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS)) {