Re: [PATCH net 1/3] bridge: br_nd_send: linearize skb before parsing ND options

[Nikolay Aleksandrov <razor@blackwall.org>]

On 26/03/2026 05:44, Yang Yang wrote:
> br_nd_send() parses neighbour discovery options from ns->opt[] and
> assumes that these options are in the linear part of request.
> 
> Its callers only guarantee that the ICMPv6 header and target address
> are available, so the option area can still be non-linear. Parsing
> ns->opt[] in that case can access data past the linear buffer.
> 
> Linearize request before option parsing and derive ns from the linear
> network header.
> 
> Fixes: ed842faeb2bd ("bridge: suppress nd pkts on BR_NEIGH_SUPPRESS ports")
> Reported-by: Yifan Wu <yifanwucs@gmail.com>
> Reported-by: Juefei Pu <tomapufckgml@gmail.com>
> Tested-by: Ao Zhou <n05ec@lzu.edu.cn>
> Co-developed-by: Yuan Tan <tanyuan98@outlook.com>
> Signed-off-by: Yuan Tan <tanyuan98@outlook.com>
> Suggested-by: Xin Liu <bird@lzu.edu.cn>
> Signed-off-by: Yang Yang <n05ec@lzu.edu.cn>
> ---
>   net/bridge/br_arp_nd_proxy.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/net/bridge/br_arp_nd_proxy.c b/net/bridge/br_arp_nd_proxy.c
> index 1e2b51769eec8..af3d1e33f50b8 100644
> --- a/net/bridge/br_arp_nd_proxy.c
> +++ b/net/bridge/br_arp_nd_proxy.c
> @@ -251,12 +251,12 @@ struct nd_msg *br_is_nd_neigh_msg(const struct sk_buff *skb, struct nd_msg *msg)
>   
>   static void br_nd_send(struct net_bridge *br, struct net_bridge_port *p,
>   		       struct sk_buff *request, struct neighbour *n,
> -		       __be16 vlan_proto, u16 vlan_tci, struct nd_msg *ns)
> +		       __be16 vlan_proto, u16 vlan_tci)
>   {
>   	struct net_device *dev = request->dev;
>   	struct net_bridge_vlan_group *vg;
> +	struct nd_msg *na, *ns;
>   	struct sk_buff *reply;
> -	struct nd_msg *na;
>   	struct ipv6hdr *pip6;
>   	int na_olen = 8; /* opt hdr + ETH_ALEN for target */
>   	int ns_olen;
> @@ -264,7 +264,7 @@ static void br_nd_send(struct net_bridge *br, struct net_bridge_port *p,
>   	u8 *daddr;
>   	u16 pvid;
>   
> -	if (!dev)
> +	if (!dev || skb_linearize(request))
>   		return;
>   
>   	len = LL_RESERVED_SPACE(dev) + sizeof(struct ipv6hdr) +
> @@ -281,6 +281,8 @@ static void br_nd_send(struct net_bridge *br, struct net_bridge_port *p,
>   	skb_set_mac_header(reply, 0);
>   
>   	daddr = eth_hdr(request)->h_source;
> +	ns = (struct nd_msg *)(skb_network_header(request) +
> +			       sizeof(struct ipv6hdr));
>   
>   	/* Do we need option processing ? */
>   	ns_olen = request->len - (skb_network_offset(request) +
> @@ -472,9 +474,9 @@ void br_do_suppress_nd(struct sk_buff *skb, struct net_bridge *br,
>   				if (vid != 0)
>   					br_nd_send(br, p, skb, n,
>   						   skb->vlan_proto,
> -						   skb_vlan_tag_get(skb), msg);
> +						   skb_vlan_tag_get(skb));
>   				else
> -					br_nd_send(br, p, skb, n, 0, 0, msg);
> +					br_nd_send(br, p, skb, n, 0, 0);
>   				replied = true;
>   			}
>   

Acked-by: Nikolay Aleksandrov <razor@blackwall.org>