From 96106a207ae972d8f9e4815e84c159f29e4bbee7 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 2 Nov 2016 19:00:40 -0700 Subject: [PATCH 1/1] dccp: fix out of bound access in dccp_v4_err() [ Upstream commit 6706a97fec963d6cb3f7fc2978ec1427b4651214 ] dccp_v4_err() does not use pskb_may_pull() and might access garbage. We only need 4 bytes at the beginning of the DCCP header, like TCP, so the 8 bytes pulled in icmp_socket_deliver() are more than enough. This patch might allow to process more ICMP messages, as some routers are still limiting the size of reflected bytes to 28 (RFC 792), instead of extended lengths (RFC 1812 4.3.2.3) Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller [bwh: Backported to 3.2: use offsetof() + sizeof() instead of offsetofend()] Signed-off-by: Ben Hutchings --- net/dccp/ipv4.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c index d336501f3451..76e04064d057 100644 --- a/net/dccp/ipv4.c +++ b/net/dccp/ipv4.c @@ -211,7 +211,7 @@ static void dccp_v4_err(struct sk_buff *skb, u32 info) { const struct iphdr *iph = (struct iphdr *)skb->data; const u8 offset = iph->ihl << 2; - const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data + offset); + const struct dccp_hdr *dh; struct dccp_sock *dp; struct inet_sock *inet; const int type = icmp_hdr(skb)->type; @@ -221,11 +221,13 @@ static void dccp_v4_err(struct sk_buff *skb, u32 info) int err; struct net *net = dev_net(skb->dev); - if (skb->len < offset + sizeof(*dh) || - skb->len < offset + __dccp_basic_hdr_len(dh)) { - ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); - return; - } + /* Only need dccph_dport & dccph_sport which are the first + * 4 bytes in dccp header. + * Our caller (icmp_socket_deliver()) already pulled 8 bytes for us. + */ + BUILD_BUG_ON(offsetof(struct dccp_hdr, dccph_sport) + sizeof(dh->dccph_sport) > 8); + BUILD_BUG_ON(offsetof(struct dccp_hdr, dccph_dport) + sizeof(dh->dccph_dport) > 8); + dh = (struct dccp_hdr *)(skb->data + offset); sk = inet_lookup(net, &dccp_hashinfo, iph->daddr, dh->dccph_dport, -- 2.39.2