From 04a6b8bfee06e309be7e9ae4527cdab19c081761 Mon Sep 17 00:00:00 2001 From: Mathias Krause Date: Fri, 11 Sep 2015 09:57:20 +0200 Subject: [PATCH] xfrm6: Fix ICMPv6 and MH header checks in _decode_session6 Ensure there's enough data left prior calling pskb_may_pull(). If skb->data was already advanced, we'll call pskb_may_pull() with a negative value converted to unsigned int -- leading to a huge positive value. That won't matter in practice as pskb_may_pull() will likely fail in this case, but it leads to underflow reports on kernels handling such kind of over-/underflows, e.g. a PaX enabled kernel instrumented with the size_overflow plugin. Reported-by: satmd Reported-and-tested-by: Marcin Jurkowski Signed-off-by: Mathias Krause Cc: PaX Team Signed-off-by: Steffen Klassert --- net/ipv6/xfrm6_policy.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c index 30caa289c5db..f10b9400b6d7 100644 --- a/net/ipv6/xfrm6_policy.c +++ b/net/ipv6/xfrm6_policy.c @@ -178,7 +178,8 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse) return; case IPPROTO_ICMPV6: - if (!onlyproto && pskb_may_pull(skb, nh + offset + 2 - skb->data)) { + if (!onlyproto && (nh + offset + 2 < skb->data || + pskb_may_pull(skb, nh + offset + 2 - skb->data))) { u8 *icmp; nh = skb_network_header(skb); @@ -192,7 +193,8 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse) #if IS_ENABLED(CONFIG_IPV6_MIP6) case IPPROTO_MH: offset += ipv6_optlen(exthdr); - if (!onlyproto && pskb_may_pull(skb, nh + offset + 3 - skb->data)) { + if (!onlyproto && (nh + offset + 3 < skb->data || + pskb_may_pull(skb, nh + offset + 3 - skb->data))) { struct ip6_mh *mh; nh = skb_network_header(skb); -- 2.20.1