netdev - [PATCH v2] xfrm6: call kfree

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Date:   Fri, 31 Aug 2018 08:38:49 -0300
From:   Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
To:     netdev@...r.kernel.org
Cc:     yoshfuji@...ux-ipv6.org, kuznet@....inr.ac.ru, davem@...emloft.net,
        herbert@...dor.apana.org.au, steffen.klassert@...unet.com,
        eyal.birger@...il.com, sd@...asysnail.net, cascardo@...onical.com
Subject: [PATCH v2] xfrm6: call kfree_skb when skb is toobig

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 <cascardo@...onical.com>
Reviewed-by: Sabrina Dubroca <sd@...asysnail.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