From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        =?UTF-8?q?Ignacy=20Gaw=C4=99dzki?= 
        <ignacy.gawedzki@green-communications.fr>,
        Florian Westphal <fw@strlen.de>,
        Pablo Neira Ayuso <pablo@netfilter.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10 14/76] netfilter: fix regression in looped (broad|multi)casts MAC handling
Date:   Mon, 27 Dec 2021 16:30:29 +0100
Message-Id: <20211227151325.189082718@linuxfoundation.org>
In-Reply-To: <20211227151324.694661623@linuxfoundation.org>
References: <20211227151324.694661623@linuxfoundation.org>
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From: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>

[ Upstream commit ebb966d3bdfed581ecccbb4a7432341baf7619b4 ]

In commit 5648b5e1169f ("netfilter: nfnetlink_queue: fix OOB when mac
header was cleared"), the test for non-empty MAC header introduced in
commit 2c38de4c1f8da7 ("netfilter: fix looped (broad|multi)cast's MAC
handling") has been replaced with a test for a set MAC header.

This breaks the case when the MAC header has been reset (using
skb_reset_mac_header), as is the case with looped-back multicast
packets.  As a result, the packets ending up in NFQUEUE get a bogus
hwaddr interpreted from the first bytes of the IP header.

This patch adds a test for a non-empty MAC header in addition to the
test for a set MAC header.  The same two tests are also implemented in
nfnetlink_log.c, where the initial code of commit 2c38de4c1f8da7
("netfilter: fix looped (broad|multi)cast's MAC handling") has not been
touched, but where supposedly the same situation may happen.

Fixes: 5648b5e1169f ("netfilter: nfnetlink_queue: fix OOB when mac header was cleared")
Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/netfilter/nfnetlink_log.c   | 3 ++-
 net/netfilter/nfnetlink_queue.c | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index b35e8d9a5b37e..33c13edbca4bb 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -557,7 +557,8 @@ __build_packet_message(struct nfnl_log_net *log,
 		goto nla_put_failure;
 
 	if (indev && skb->dev &&
-	    skb->mac_header != skb->network_header) {
+	    skb_mac_header_was_set(skb) &&
+	    skb_mac_header_len(skb) != 0) {
 		struct nfulnl_msg_packet_hw phw;
 		int len;
 
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index 98994fe677fe9..b0358f30947ea 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -562,7 +562,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 		goto nla_put_failure;
 
 	if (indev && entskb->dev &&
-	    skb_mac_header_was_set(entskb)) {
+	    skb_mac_header_was_set(entskb) &&
+	    skb_mac_header_len(entskb) != 0) {
 		struct nfqnl_msg_packet_hw phw;
 		int len;
 
-- 
2.34.1