[ 050/120] ipv6: mip6: fix mip6_mh_filter()

Greg Kroah-Hartman
2012-10-11T01:23:05Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 96af69ea2a83d292238bdba20e4508ee967cf8cb ]

mip6_mh_filter() should not modify its input, or else its caller
would need to recompute ipv6_hdr() if skb->head is reallocated.

Use skb_header_pointer() instead of pskb_may_pull()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/mip6.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)

--- a/net/ipv6/mip6.c
+++ b/net/ipv6/mip6.c
@@ -84,28 +84,30 @@ static int mip6_mh_len(int type)

static int mip6_mh_filter(struct sock *sk, struct sk_buff *skb)
{
- struct ip6_mh *mh;
+ struct ip6_mh _hdr;
+ const struct ip6_mh *mh;

- if (!pskb_may_pull(skb, (skb_transport_offset(skb)) + 8) ||
- !pskb_may_pull(skb, (skb_transport_offset(skb) +
- ((skb_transport_header(skb)[1] + 1) << 3))))
+ mh = skb_header_pointer(skb, skb_transport_offset(skb),
+ sizeof(_hdr), &_hdr);
+ if (!mh)
return -1;

- mh = (struct ip6_mh *)skb_transport_header(skb);
+ if (((mh->ip6mh_hdrlen + 1) << 3) > skb->len)
+ return -1;

if (mh->ip6mh_hdrlen < mip6_mh_len(mh->ip6mh_type)) {
LIMIT_NETDEBUG(KERN_DEBUG "mip6: MH message too short: %d vs >=%d\n",
mh->ip6mh_hdrlen, mip6_mh_len(mh->ip6mh_type));
- mip6_param_prob(skb, 0, ((&mh->ip6mh_hdrlen) -
- skb_network_header(skb)));
+ mip6_param_prob(skb, 0, offsetof(struct ip6_mh, ip6mh_hdrlen) +
+ skb_network_header_len(skb));
return -1;
}

if (mh->ip6mh_proto != IPPROTO_NONE) {
LIMIT_NETDEBUG(KERN_DEBUG "mip6: MH invalid payload proto = %d\n",
mh->ip6mh_proto);
- mip6_param_prob(skb, 0, ((&mh->ip6mh_proto) -
- skb_network_header(skb)));
+ mip6_param_prob(skb, 0, offsetof(struct ip6_mh, ip6mh_proto) +
+ skb_network_header_len(skb));
return -1;
}