netdev - [PATCH net-next 1/5] ipv6: Check if max HBH or DestOp sysctl is zero and drop if it is

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Message-ID: <20251201185817.1003392-2-tom@herbertland.com>
Date: Mon,  1 Dec 2025 10:55:30 -0800
From: Tom Herbert <tom@...bertland.com>
To: tom@...bertland.com,
	davem@...emloft.net,
	kuba@...nel.org,
	netdev@...r.kernel.org
Subject: [PATCH net-next 1/5] ipv6: Check if max HBH or DestOp sysctl is zero and drop if it is

In IPv6 Destination options processing function check if
net->ipv6.sysctl.max_dst_opts_cnt is zero up front. If is zero then
drop the packet since Destination Options processing is disabled.

Similarly, in IPv6 hop-by-hop options processing function check if
net->ipv6.sysctl.max_hbh_opts_cnt is zero up front. If is zero then
drop the packet since Hop-by-Hop Options processing is disabled.
---
 net/ipv6/exthdrs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index a23eb8734e15..11ff3d4df129 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -303,7 +303,8 @@ static int ipv6_destopt_rcv(struct sk_buff *skb)
 	struct net *net = dev_net(skb->dev);
 	int extlen;
 
-	if (!pskb_may_pull(skb, skb_transport_offset(skb) + 8) ||
+	if (!net->ipv6.sysctl.max_dst_opts_cnt ||
+	    !pskb_may_pull(skb, skb_transport_offset(skb) + 8) ||
 	    !pskb_may_pull(skb, (skb_transport_offset(skb) +
 				 ((skb_transport_header(skb)[1] + 1) << 3)))) {
 		__IP6_INC_STATS(dev_net(dst_dev(dst)), idev,
@@ -1040,7 +1041,8 @@ int ipv6_parse_hopopts(struct sk_buff *skb)
 	 * sizeof(struct ipv6hdr) by definition of
 	 * hop-by-hop options.
 	 */
-	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr) + 8) ||
+	if (!net->ipv6.sysctl.max_hbh_opts_cnt ||
+	    !pskb_may_pull(skb, sizeof(struct ipv6hdr) + 8) ||
 	    !pskb_may_pull(skb, (sizeof(struct ipv6hdr) +
 				 ((skb_transport_header(skb)[1] + 1) << 3)))) {
 fail_and_free:
-- 
2.43.0