[PATCH] netfilter: nf_queue: reject NF_STOLEN verdicts from userspace

[PATCH] netfilter: nf_queue: reject NF_STOLEN verdicts from userspace

[Florian Westphal]

A userspace listener may send (bogus) NF_STOLEN verdict, which causes skb leak.

This problem was previously fixed via
64507fdbc29c3a622180378210ecea8659b14e40 (netfilter:
nf_queue: fix NF_STOLEN skb leak) but this had to be reverted because
NF_STOLEN can also be returned by a netfilter hook when iterating the
rules in nf_reinject.

Reject userspace NF_STOLEN verdict, as suggested by Michał Mirosław.

This is complementary to commit fad54440438a7c231a6ae347738423cbabc936d9
(netfilter: avoid double free in nf_reinject).

Cc: Julian Anastasov <ja@ssi.bg>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/ipv4/netfilter/ip_queue.c   |   11 ++++-------
 net/ipv6/netfilter/ip6_queue.c  |   11 ++++-------
 net/netfilter/nfnetlink_queue.c |    4 ++--
 3 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/net/ipv4/netfilter/ip_queue.c b/net/ipv4/netfilter/ip_queue.c
index d2c1311..8ad0bb1 100644
--- a/net/ipv4/netfilter/ip_queue.c
+++ b/net/ipv4/netfilter/ip_queue.c
@@ -312,7 +312,7 @@ ipq_set_verdict(struct ipq_verdict_msg *vmsg, unsigned int len)
 {
 	struct nf_queue_entry *entry;
 
-	if (vmsg->value > NF_MAX_VERDICT)
+	if (vmsg->value > NF_MAX_VERDICT || vmsg->value == NF_STOLEN)
 		return -EINVAL;
 
 	entry = ipq_find_dequeue_entry(vmsg->id);
@@ -357,12 +357,9 @@ ipq_receive_peer(struct ipq_peer_msg *pmsg,
 		break;
 
 	case IPQM_VERDICT:
-		if (pmsg->msg.verdict.value > NF_MAX_VERDICT)
-			status = -EINVAL;
-		else
-			status = ipq_set_verdict(&pmsg->msg.verdict,
-						 len - sizeof(*pmsg));
-			break;
+		status = ipq_set_verdict(&pmsg->msg.verdict,
+					 len - sizeof(*pmsg));
+		break;
 	default:
 		status = -EINVAL;
 	}
diff --git a/net/ipv6/netfilter/ip6_queue.c b/net/ipv6/netfilter/ip6_queue.c
index 413ab07..974d07f 100644
--- a/net/ipv6/netfilter/ip6_queue.c
+++ b/net/ipv6/netfilter/ip6_queue.c
@@ -312,7 +312,7 @@ ipq_set_verdict(struct ipq_verdict_msg *vmsg, unsigned int len)
 {
 	struct nf_queue_entry *entry;
 
-	if (vmsg->value > NF_MAX_VERDICT)
+	if (vmsg->value > NF_MAX_VERDICT || vmsg->value == NF_STOLEN)
 		return -EINVAL;
 
 	entry = ipq_find_dequeue_entry(vmsg->id);
@@ -357,12 +357,9 @@ ipq_receive_peer(struct ipq_peer_msg *pmsg,
 		break;
 
 	case IPQM_VERDICT:
-		if (pmsg->msg.verdict.value > NF_MAX_VERDICT)
-			status = -EINVAL;
-		else
-			status = ipq_set_verdict(&pmsg->msg.verdict,
-						 len - sizeof(*pmsg));
-			break;
+		status = ipq_set_verdict(&pmsg->msg.verdict,
+					 len - sizeof(*pmsg));
+		break;
 	default:
 		status = -EINVAL;
 	}
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index fbfcd83..89cb76a 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -645,8 +645,8 @@ verdicthdr_get(const struct nlattr * const nfqa[])
 		return NULL;
 
 	vhdr = nla_data(nfqa[NFQA_VERDICT_HDR]);
-	verdict = ntohl(vhdr->verdict);
-	if ((verdict & NF_VERDICT_MASK) > NF_MAX_VERDICT)
+	verdict = ntohl(vhdr->verdict) & NF_VERDICT_MASK;
+	if (verdict > NF_MAX_VERDICT || verdict == NF_STOLEN)
 		return NULL;
 	return vhdr;
 }
-- 
1.7.3.4

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Re: [PATCH] netfilter: nf_queue: reject NF_STOLEN verdicts from userspace

[Patrick McHardy]

On 12.08.2011 22:34, Florian Westphal wrote:
> A userspace listener may send (bogus) NF_STOLEN verdict, which causes skb leak.
> 
> This problem was previously fixed via
> 64507fdbc29c3a622180378210ecea8659b14e40 (netfilter:
> nf_queue: fix NF_STOLEN skb leak) but this had to be reverted because
> NF_STOLEN can also be returned by a netfilter hook when iterating the
> rules in nf_reinject.
> 
> Reject userspace NF_STOLEN verdict, as suggested by Michał Mirosław.
> 
> This is complementary to commit fad54440438a7c231a6ae347738423cbabc936d9
> (netfilter: avoid double free in nf_reinject).
> 
> Cc: Julian Anastasov <ja@ssi.bg>
> Cc: Eric Dumazet <eric.dumazet@gmail.com>
> Signed-off-by: Florian Westphal <fw@strlen.de>

Applied, thanks Florian.
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