[PATCH 3.10 226/319] ipv6: dccp: fix out of bound access in dccp_v6_err()

Willy Tarreau
2017-02-05T19:41:59Z

From: Eric Dumazet <edumazet@google.com>

commit 1aa9d1a0e7eefcc61696e147d123453fc0016005 upstream.

dccp_v6_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 icmpv6_notify() are more than enough.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
net/dccp/ipv6.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 6cf9f77..fb72107 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -83,7 +83,7 @@ static void dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
u8 type, u8 code, int offset, __be32 info)
{
const struct ipv6hdr *hdr = (const struct ipv6hdr *)skb->data;
- const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data + offset);
+ const struct dccp_hdr *dh;
struct dccp_sock *dp;
struct ipv6_pinfo *np;
struct sock *sk;
@@ -91,12 +91,13 @@ static void dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
__u64 seq;
struct net *net = dev_net(skb->dev);

- if (skb->len < offset + sizeof(*dh) ||
- skb->len < offset + __dccp_basic_hdr_len(dh)) {
- ICMP6_INC_STATS_BH(net, __in6_dev_get(skb->dev),
- ICMP6_MIB_INERRORS);
- return;
- }
+ /* Only need dccph_dport & dccph_sport which are the first
+ * 4 bytes in dccp header.
+ * Our caller (icmpv6_notify()) already pulled 8 bytes for us.
+ */
+ BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_sport) > 8);
+ BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_dport) > 8);
+ dh = (struct dccp_hdr *)(skb->data + offset);

sk = inet6_lookup(net, &dccp_hashinfo,
&hdr->daddr, dh->dccph_dport,
--
2.8.0.rc2.1.gbe9624a