linux-kernel - RE: NULL Pointer Deference: NFS & Telnet

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Date:	Tue, 25 May 2010 21:02:51 -0500
From:	"Arce, Abraham" <x0066660@...com>
To:	David Miller <davem@...emloft.net>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"tony@...mide.com" <tony@...mide.com>,
	"Shilimkar, Santosh" <santosh.shilimkar@...com>
Subject: RE: NULL Pointer Deference: NFS & Telnet

Thanks David,

> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index f8abf68..eb81f76 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -334,7 +334,7 @@ static void skb_release_data(struct sk_buff *skb)
> >  	if (!skb->cloned ||
> >  	    !atomic_sub_return(skb->nohdr ? (1 << SKB_DATAREF_SHIFT) + 1 : 1,
> >  			       &skb_shinfo(skb)->dataref)) {
> > -		if (skb_shinfo(skb)->nr_frags) {
> > +		if (skb_shinfo(skb)->nr_frags && skb_has_frags(skb)) {
> >  			int i;
> >  			for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
> >  				put_page(skb_shinfo(skb)->frags[i].page);
> 
> skb_shinfo(skb)->nr_frags counts the number of entries contained
> in the skb_shinfo(skb)->frags[] array.
> 
> This has nothing to do with the frag list pointer,
> skb_shinfo(skb)->frag_list, which is what skb_has_frags()
> tests.
> 
> You've got some kind of memory corruption going on and it
> appears to have nothing to do with the code paths you're
> playing with here.

Do you have any recommendation on debugging technique/tool for this memory corruption issue?

Best Regards
Abraham
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