netdev - Re: [RFC PATCH] udp: don't rereference dst

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Date:	Thu, 14 Mar 2013 16:29:06 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Parkin <tparkin@...alix.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [RFC PATCH] udp: don't rereference dst_entry dev pointer on rcv

On Thu, 2013-03-14 at 16:05 +0100, Eric Dumazet wrote:
> On Thu, 2013-03-14 at 14:45 +0000, Tom Parkin wrote:
> > On Thu, Mar 14, 2013 at 02:18:04AM +0100, Eric Dumazet wrote:
> > > Ah thanks for this, as this definitely makes more sense ;)
> > > 
> > > Could you try the following fix ?
> > > 
> > > diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
> > > index b6d30ac..87f4ecb 100644
> > > --- a/net/ipv4/ip_fragment.c
> > > +++ b/net/ipv4/ip_fragment.c
> > > @@ -529,6 +529,7 @@ found:
> > >  	    qp->q.meat == qp->q.len)
> > >  		return ip_frag_reasm(qp, prev, dev);
> > >  
> > > +	skb_dst_force(skb);
> > >  	inet_frag_lru_move(&qp->q);
> > >  	return -EINPROGRESS;
> > >
> > 
> > Thanks Eric, with this patch I can no longer reproduce the oops :-)
> 
> Thanks for testing.
> 
> I am considering an alternative patch :
> 
> We can drop the reference instead, and use the dst of the last skb.
> 
> This would help to not dirty the dst refcount.
> 
> I'll send an updated version.
> 

OK, I tested the following one instead, please test it so that I can send an official patch.

Thanks

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index b6d30ac..2d23830 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -529,6 +529,7 @@ found:
 	    qp->q.meat == qp->q.len)
 		return ip_frag_reasm(qp, prev, dev);
 
+	skb_dst_drop(skb);
 	inet_frag_lru_move(&qp->q);
 	return -EINPROGRESS;
 


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