netdev - [PATCH net-next 2/9] netfilter: bridge: call pskb_may_pull in br_nf_check_hbh

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Message-Id: <20230308193033.13965-3-fw@strlen.de>
Date:   Wed,  8 Mar 2023 20:30:26 +0100
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>, Xin Long <lucien.xin@...il.com>,
        Simon Horman <simon.horman@...igine.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Aaron Conole <aconole@...hat.com>
Subject: [PATCH net-next 2/9] netfilter: bridge: call pskb_may_pull in br_nf_check_hbh_len

From: Xin Long <lucien.xin@...il.com>

When checking Hop-by-hop option header, if the option data is in
nonlinear area, it should do pskb_may_pull instead of discarding
the skb as a bad IPv6 packet.

Signed-off-by: Xin Long <lucien.xin@...il.com>
Reviewed-by: Simon Horman <simon.horman@...igine.com>
Acked-by: Nikolay Aleksandrov <razor@...ckwall.org>
Reviewed-by: Aaron Conole <aconole@...hat.com>
Signed-off-by: Florian Westphal <fw@...len.de>
---
 net/bridge/br_netfilter_ipv6.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/net/bridge/br_netfilter_ipv6.c b/net/bridge/br_netfilter_ipv6.c
index 6b07f30675bb..afd1c718b683 100644
--- a/net/bridge/br_netfilter_ipv6.c
+++ b/net/bridge/br_netfilter_ipv6.c
@@ -45,14 +45,18 @@
  */
 static int br_nf_check_hbh_len(struct sk_buff *skb)
 {
-	unsigned char *raw = (u8 *)(ipv6_hdr(skb) + 1);
+	int len, off = sizeof(struct ipv6hdr);
+	unsigned char *nh;
 	u32 pkt_len;
-	const unsigned char *nh = skb_network_header(skb);
-	int off = raw - nh;
-	int len = (raw[1] + 1) << 3;
 
-	if ((raw + len) - skb->data > skb_headlen(skb))
+	if (!pskb_may_pull(skb, off + 8))
 		goto bad;
+	nh = (unsigned char *)(ipv6_hdr(skb) + 1);
+	len = (nh[1] + 1) << 3;
+
+	if (!pskb_may_pull(skb, off + len))
+		goto bad;
+	nh = skb_network_header(skb);
 
 	off += 2;
 	len -= 2;
-- 
2.39.2