[PATCH v2] xfrm6: call kfree_skb when skb is toobig

[Thadeu Lima de Souza Cascardo]

After commit d6990976af7c5d8f55903bfb4289b6fb030bf754 ("vti6: fix PMTU caching
and reporting on xmit"), some too big skbs might be potentially passed down to
__xfrm6_output, causing it to fail to transmit but not free the skb, causing a
leak of skb, and consequentially a leak of dst references.

After running pmtu.sh, that shows as failure to unregister devices in a 
namespace:

[  311.397671] unregister_netdevice: waiting for veth_b to become free. Usage 
count = 1

The fix is to call kfree_skb in case of transmit failures.

Signed-off-by: Thadeu Lima de Souza Cascardo <casca...@canonical.com>
Reviewed-by: Sabrina Dubroca <s...@queasysnail.net>
Fixes: dd767856a36e ("xfrm6: Don't call icmpv6_send on local error")
---
 net/ipv6/xfrm6_output.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv6/xfrm6_output.c b/net/ipv6/xfrm6_output.c
index 5959ce9620eb..6a74080005cf 100644
--- a/net/ipv6/xfrm6_output.c
+++ b/net/ipv6/xfrm6_output.c
@@ -170,9 +170,11 @@ static int __xfrm6_output(struct net *net, struct sock 
*sk, struct sk_buff *skb)
 
        if (toobig && xfrm6_local_dontfrag(skb)) {
                xfrm6_local_rxpmtu(skb, mtu);
+               kfree_skb(skb);
                return -EMSGSIZE;
        } else if (!skb->ignore_df && toobig && skb->sk) {
                xfrm_local_error(skb, mtu);
+               kfree_skb(skb);
                return -EMSGSIZE;
        }
 
-- 
2.17.1