[PATCH 4.4 75/78] xen/netback: Reset nr_frags before freeing skb

[Greg Kroah-Hartman]

From: Ross Lagerwall <ross.lagerw...@citrix.com>

[ Upstream commit 3a0233ddec554b886298de2428edb5c50a20e694 ]

At this point nr_frags has been incremented but the frag does not yet
have a page assigned so freeing the skb results in a crash. Reset
nr_frags before freeing the skb to prevent this.

Signed-off-by: Ross Lagerwall <ross.lagerw...@citrix.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/net/xen-netback/netback.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1421,6 +1421,7 @@ static void xenvif_tx_build_gops(struct
                        skb_shinfo(skb)->nr_frags = MAX_SKB_FRAGS;
                        nskb = xenvif_alloc_skb(0);
                        if (unlikely(nskb == NULL)) {
+                               skb_shinfo(skb)->nr_frags = 0;
                                kfree_skb(skb);
                                xenvif_tx_err(queue, &txreq, idx);
                                if (net_ratelimit())
@@ -1436,6 +1437,7 @@ static void xenvif_tx_build_gops(struct
 
                        if (xenvif_set_skb_gso(queue->vif, skb, gso)) {
                                /* Failure in xenvif_set_skb_gso is fatal. */
+                               skb_shinfo(skb)->nr_frags = 0;
                                kfree_skb(skb);
                                kfree_skb(nskb);
                                break;