netdev - [PATCH net-next 1/6] netfilter: nft_exthdr: Search chunks in SCTP packets only

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Date:   Wed, 23 Jun 2021 19:02:56 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org, kuba@...nel.org
Subject: [PATCH net-next 1/6] netfilter: nft_exthdr: Search chunks in SCTP packets only

From: Phil Sutter <phil@....cc>

Since user space does not generate a payload dependency, plain sctp
chunk matches cause searching in non-SCTP packets, too. Avoid this
potential mis-interpretation of packet data by checking pkt->tprot.

Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks")
Signed-off-by: Phil Sutter <phil@....cc>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nft_exthdr.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
index 7f705b5c09de..9cf86be2cff4 100644
--- a/net/netfilter/nft_exthdr.c
+++ b/net/netfilter/nft_exthdr.c
@@ -312,6 +312,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
 	const struct sctp_chunkhdr *sch;
 	struct sctp_chunkhdr _sch;
 
+	if (pkt->tprot != IPPROTO_SCTP)
+		goto err;
+
 	do {
 		sch = skb_header_pointer(pkt->skb, offset, sizeof(_sch), &_sch);
 		if (!sch || !sch->length)
@@ -334,7 +337,7 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
 		}
 		offset += SCTP_PAD4(ntohs(sch->length));
 	} while (offset < pkt->skb->len);
-
+err:
 	if (priv->flags & NFT_EXTHDR_F_PRESENT)
 		nft_reg_store8(dest, false);
 	else
-- 
2.30.2