From a6d4518da371b0d21512ef0f641928d6f99ee70f Mon Sep 17 00:00:00 2001 From: Li RongQing Date: Sat, 18 Oct 2014 17:33:38 +0800 Subject: [PATCH] ipv6: fix a potential use after free in sit.c pskb_may_pull() maybe change skb->data and make iph pointer oboslete, fix it by geting ip header length directly. Fixes: ca15a078 (sit: generate icmpv6 error when receiving icmpv4 error) Cc: Oussama Ghorbel Signed-off-by: Li RongQing Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv6/sit.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c index 6eab37cf5345..58e5b4710127 100644 --- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -485,11 +485,11 @@ static void ipip6_tunnel_uninit(struct net_device *dev) */ static int ipip6_err_gen_icmpv6_unreach(struct sk_buff *skb) { - const struct iphdr *iph = (const struct iphdr *) skb->data; + int ihl = ((const struct iphdr *)skb->data)->ihl*4; struct rt6_info *rt; struct sk_buff *skb2; - if (!pskb_may_pull(skb, iph->ihl * 4 + sizeof(struct ipv6hdr) + 8)) + if (!pskb_may_pull(skb, ihl + sizeof(struct ipv6hdr) + 8)) return 1; skb2 = skb_clone(skb, GFP_ATOMIC); @@ -498,7 +498,7 @@ static int ipip6_err_gen_icmpv6_unreach(struct sk_buff *skb) return 1; skb_dst_drop(skb2); - skb_pull(skb2, iph->ihl * 4); + skb_pull(skb2, ihl); skb_reset_network_header(skb2); rt = rt6_lookup(dev_net(skb->dev), &ipv6_hdr(skb2)->saddr, NULL, 0, 0); -- 2.20.1