netdev - Re: [PATCH] udp: Fix potential wrong ip

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Date:	Fri, 06 Feb 2009 11:49:22 +0100
From:	Jesper Dangaard Brouer <jdb@...x.dk>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] udp: Fix potential wrong ip_hdr(skb) pointers

On Fri, 2009-02-06 at 11:04 +0100, Eric Dumazet wrote:
> Jesper Dangaard Brouer a écrit :
> > On Fri, 2009-02-06 at 01:08 -0800, David Miller wrote:
> >> Please respin this patch of your's with proper commit message
> >> and signoffs, thanks!
> > 
> > Like the UDP header fix, pskb_may_pull() can potentially
> > alter the SKB buffer.  Thus the saddr and daddr, pointers
> > may point to the old skb->data buffer.
> > 
> 
> I dont know... daddr and saddr are not pointers but integers.

Yes, you are right... its only in the ipv6 code these are pointers
(which as DaveM mentioned handels it correctly).

> Patch makes sense as a cleanup, but ChangeLog seems wrong ?

Okay, lets view it as a cleanup... Its upto DaveM if he wants to fix the
commit message (or ask me the correct it, revert and reapply...)


> > I haven't seen corruptions, as its only seen if the old
> > skb->data buffer were reallocated by another user and
> > written into very quickly (or poison'd by SLAB debugging).
> > 
> > Signed-off-by: Jesper Dangaard Brouer <hawk@...x.dk>
> > ---
> > 
> >  net/ipv4/udp.c |    6 ++++--
> >  1 files changed, 4 insertions(+), 2 deletions(-)
> > 
> > 
> > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> > index cc3a0a0..c47c989 100644
> > --- a/net/ipv4/udp.c
> > +++ b/net/ipv4/udp.c
> > @@ -1234,8 +1234,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
> >  	struct udphdr *uh;
> >  	unsigned short ulen;
> >  	struct rtable *rt = (struct rtable*)skb->dst;
> > -	__be32 saddr = ip_hdr(skb)->saddr;
> > -	__be32 daddr = ip_hdr(skb)->daddr;
> > +	__be32 saddr, daddr;
> >  	struct net *net = dev_net(skb->dev);
> >  
> >  	/*
> > @@ -1259,6 +1258,9 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
> >  	if (udp4_csum_init(skb, uh, proto))
> >  		goto csum_error;
> >  
> > +	saddr = ip_hdr(skb)->saddr;
> > +	daddr = ip_hdr(skb)->daddr;
> > +
> >  	if (rt->rt_flags & (RTCF_BROADCAST|RTCF_MULTICAST))
> >  		return __udp4_lib_mcast_deliver(net, skb, uh,
> >  				saddr, daddr, udptable);
> > 
> >
> 
> 
-- 
Med venlig hilsen / Best regards
  Jesper Brouer
  ComX Networks A/S
  Linux Network developer
  Cand. Scient Datalog / MSc.
  Author of http://adsl-optimizer.dk
  LinkedIn: http://www.linkedin.com/in/brouer
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