On Thu, 30 Dec 2010 19:52:14 +0100
Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote:
> On Thu, 2010-12-30 at 10:46 -0800, Stephen Hemminger wrote:
>
> > This doesn't look correct. The calculation of the offset doesn't look correct.
> > Just following the skb_clone(), the skb_pull value is "offset".
> > Also, the other checks return -EINVAL for incorrectly formed packet.
> >
> > --- a/net/bridge/br_multicast.c 2010-12-30 10:29:58.579510488 -0800
> > +++ b/net/bridge/br_multicast.c 2010-12-30 10:43:27.273386691 -0800
> > @@ -1464,6 +1464,9 @@ static int br_multicast_ipv6_rcv(struct
> > if (offset < 0 || nexthdr != IPPROTO_ICMPV6)
> > return 0;
> >
> > + if (!pskb_may_pull(skb, offset))
> > + return -EINVAL;
> > +
> > /* Okay, we found ICMPv6 header */
> > skb2 = skb_clone(skb, GFP_ATOMIC);
> > if (!skb2)
>
> Wouldn't that make more sense after the clone anyway? But if you look at
> my email, you'll find that there's potentially, and conditionally, more
> stuff that will be read from the skb's header, which hasn't necessarily
> been pulled in, so I think this still won't fix all the issues.
>
> Seeing how this only affects some ICMPv6 packets, maybe we should just
> use skb_copy() instead?
It comes out cleaner, and the check can be simplified.
--- a/net/bridge/br_multicast.c 2010-12-30 10:47:12.031733855 -0800
+++ b/net/bridge/br_multicast.c 2010-12-30 11:00:12.135801266 -0800
@@ -1465,19 +1465,19 @@ static int br_multicast_ipv6_rcv(struct
return 0;
/* Okay, we found ICMPv6 header */
- skb2 = skb_clone(skb, GFP_ATOMIC);
+ skb2 = skb_copy(skb, GFP_ATOMIC);
if (!skb2)
return -ENOMEM;
+ err = -EINVAL;
+ if (skb2->len < offset + sizeof(*icmp6h))
+ goto out;
+
len -= offset - skb_network_offset(skb2);
__skb_pull(skb2, offset);
skb_reset_transport_header(skb2);
- err = -EINVAL;
- if (!pskb_may_pull(skb2, sizeof(*icmp6h)))
- goto out;
-
icmp6h = icmp6_hdr(skb2);
switch (icmp6h->icmp6_type) {
--
--
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