netdev - Re: [PATCH net 2/4] net: bridge: mcast: fix stale ipv6 hdr pointer when handling v6 query

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Message-ID: <fdd4c5d2-1872-bac5-3aa9-107e2081b18f@linuxlounge.net>
Date:   Tue, 2 Jul 2019 14:37:28 +0200
From:   Martin Weinelt <martin@...uxlounge.net>
To:     Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        netdev@...r.kernel.org
Cc:     roopa@...ulusnetworks.com, davem@...emloft.net,
        bridge@...ts.linux-foundation.org, yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH net 2/4] net: bridge: mcast: fix stale ipv6 hdr pointer
 when handling v6 query

Tested-by: Martin Weinelt <martin@...uxlounge.net>

On 7/2/19 2:00 PM, Nikolay Aleksandrov wrote:
> We get a pointer to the ipv6 hdr in br_ip6_multicast_query but we may
> call pskb_may_pull afterwards and end up using a stale pointer.
> So use the header directly, it's just 1 place where it's needed.
> 
> Fixes: 08b202b67264 ("bridge br_multicast: IPv6 MLD support.")
> Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
> ---
>  net/bridge/br_multicast.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
> index f37897e7b97b..3d8deac2353d 100644
> --- a/net/bridge/br_multicast.c
> +++ b/net/bridge/br_multicast.c
> @@ -1279,7 +1279,6 @@ static int br_ip6_multicast_query(struct net_bridge *br,
>  				  u16 vid)
>  {
>  	unsigned int transport_len = ipv6_transport_len(skb);
> -	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
>  	struct mld_msg *mld;
>  	struct net_bridge_mdb_entry *mp;
>  	struct mld2_query *mld2q;
> @@ -1323,7 +1322,7 @@ static int br_ip6_multicast_query(struct net_bridge *br,
>  
>  	if (is_general_query) {
>  		saddr.proto = htons(ETH_P_IPV6);
> -		saddr.u.ip6 = ip6h->saddr;
> +		saddr.u.ip6 = ipv6_hdr(skb)->saddr;
>  
>  		br_multicast_query_received(br, port, &br->ip6_other_query,
>  					    &saddr, max_delay);
> 




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