[PATCH 3.16.y-ckt 066/254] netfilter: nf_log: release skbuff on nlmsg put failure

[Luis Henriques]

3.16.7-ckt2 -stable review patch.  If anyone has any objections, please let me know.

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

From: Houcheng Lin <houcheng at gmail.com>

commit b51d3fa364885a2c1e1668f88776c67c95291820 upstream.

The kernel should reserve enough room in the skb so that the DONE
message can always be appended.  However, in case of e.g. new attribute
erronously not being size-accounted for, __nfulnl_send() will still
try to put next nlmsg into this full skbuf, causing the skb to be stuck
forever and blocking delivery of further messages.

Fix issue by releasing skb immediately after nlmsg_put error and
WARN() so we can track down the cause of such size mismatch.

[ fw at strlen.de: add tailroom/len info to WARN ]

Signed-off-by: Houcheng Lin <houcheng at gmail.com>
Signed-off-by: Florian Westphal <fw at strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/netfilter/nfnetlink_log.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 8f415d6889fe..dd9fb9de9f1d 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -346,26 +346,25 @@ nfulnl_alloc_skb(struct net *net, u32 peer_portid, unsigned int inst_size,
 	return skb;
 }
 
-static int
+static void
 __nfulnl_send(struct nfulnl_instance *inst)
 {
-	int status = -1;
-
 	if (inst->qlen > 1) {
 		struct nlmsghdr *nlh = nlmsg_put(inst->skb, 0, 0,
 						 NLMSG_DONE,
 						 sizeof(struct nfgenmsg),
 						 0);
-		if (!nlh)
+		if (WARN_ONCE(!nlh, "bad nlskb size: %u, tailroom %d\n",
+			      inst->skb->len, skb_tailroom(inst->skb))) {
+			kfree_skb(inst->skb);
 			goto out;
+		}
 	}
-	status = nfnetlink_unicast(inst->skb, inst->net, inst->peer_portid,
-				   MSG_DONTWAIT);
-
+	nfnetlink_unicast(inst->skb, inst->net, inst->peer_portid,
+			  MSG_DONTWAIT);
+out:
 	inst->qlen = 0;
 	inst->skb = NULL;
-out:
-	return status;
 }
 
 static void
-- 
2.1.0