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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Sabrina Dubroca" <sd@queasysnail.net>,
        "Steffen Klassert" <steffen.klassert@secunet.com>,
        "Thadeu Lima de Souza Cascardo" <cascardo@canonical.com>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
Message-ID: <lsq.1544392233.300042549@decadent.org.uk>
Subject: [PATCH 3.16 185/328] xfrm6: call kfree_skb when skb is toobig
In-Reply-To: <lsq.1544392232.713909046@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

commit 215ab0f021c9fea3c18b75e7d522400ee6a49990 upstream.

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.

Fixes: dd767856a36e ("xfrm6: Don't call icmpv6_send on local error")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 net/ipv6/xfrm6_output.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/net/ipv6/xfrm6_output.c
+++ b/net/ipv6/xfrm6_output.c
@@ -158,9 +158,11 @@ static int __xfrm6_output(struct sk_buff
 
 	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;
 	}