netdev - [PATCH net-next 4/7] netfilter: nf_nat: mask out non-verdict bits when checking return value

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Date: Wed, 18 Oct 2023 10:51:08 +0200
From: Florian Westphal <fw@...len.de>
To: <netdev@...r.kernel.org>
Cc: Paolo Abeni <pabeni@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	<netfilter-devel@...r.kernel.org>
Subject: [PATCH net-next 4/7] netfilter: nf_nat: mask out non-verdict bits when checking return value

Same as previous change: we need to mask out the non-verdict bits, as
upcoming patches may embed an errno value in NF_STOLEN verdicts too.

NF_DROP could already do this, but not all called functions do this.

Checks that only test ret vs NF_ACCEPT are fine, the 'errno parts'
are always 0 for those.

Signed-off-by: Florian Westphal <fw@...len.de>
---
 net/netfilter/nf_nat_proto.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_nat_proto.c b/net/netfilter/nf_nat_proto.c
index 5a049740758f..6d969468c779 100644
--- a/net/netfilter/nf_nat_proto.c
+++ b/net/netfilter/nf_nat_proto.c
@@ -999,11 +999,12 @@ static unsigned int
 nf_nat_ipv6_in(void *priv, struct sk_buff *skb,
 	       const struct nf_hook_state *state)
 {
-	unsigned int ret;
+	unsigned int ret, verdict;
 	struct in6_addr daddr = ipv6_hdr(skb)->daddr;
 
 	ret = nf_nat_ipv6_fn(priv, skb, state);
-	if (ret != NF_DROP && ret != NF_STOLEN &&
+	verdict = ret & NF_VERDICT_MASK;
+	if (verdict != NF_DROP && verdict != NF_STOLEN &&
 	    ipv6_addr_cmp(&daddr, &ipv6_hdr(skb)->daddr))
 		skb_dst_drop(skb);
 
-- 
2.41.0