diff mbox

[3/3] netfilter: nf_log: release skbuff on nlmsg put failure

Message ID 1414053368-29037-4-git-send-email-fw@strlen.de
State Accepted
Delegated to: Pablo Neira
Headers show

Commit Message

Florian Westphal Oct. 23, 2014, 8:36 a.m. UTC 
From: Houcheng Lin <houcheng@gmail.com>

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@strlen.de: add tailroom/len info to WARN ]

Signed-off-by: Houcheng Lin <houcheng@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nfnetlink_log.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

Comments

Pablo Neira Ayuso Oct. 24, 2014, 12:35 p.m. UTC | #1 
On Thu, Oct 23, 2014 at 10:36:08AM +0200, Florian Westphal wrote:
> From: Houcheng Lin <houcheng@gmail.com>
> 
> 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.

Good idea.

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

Applied, thanks.
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diff mbox

Patch

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 2d02eac3..5f1be5b 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