netdev - Re: bridge: Fix IGMP3 report parsing

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Message-ID: <20100408040709.GA19944@gondor.apana.org.au>
Date:	Thu, 8 Apr 2010 12:07:09 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, banyeer@...oo.com
Subject: Re: bridge: Fix IGMP3 report parsing

On Wed, Apr 07, 2010 at 08:52:48PM -0700, David Miller wrote:
> 
> If pskb_may_pull() actually does anything non-trivial,
> skb->data will change and you'll be referring to freed
> up memory.
> 
> That's probably why you had the grec assignment where
> you originally had it in the first place :-)

Heh, you're clearly more awake than I was :)

bridge: Fix IGMP3 report parsing

The IGMP3 report parsing is looking at the wrong address for
group records.  This patch fixes it.

Reported-by: Banyeer <banyeer@...oo.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 6980625..f29ada8 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -723,7 +723,7 @@ static int br_multicast_igmp3_report(struct net_bridge *br,
 		if (!pskb_may_pull(skb, len))
 			return -EINVAL;
 
-		grec = (void *)(skb->data + len);
+		grec = (void *)(skb->data + len - sizeof(*grec));
 		group = grec->grec_mca;
 		type = grec->grec_type;
 
Thanks,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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