linux-kernel - Re: 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff

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Message-ID: <Pine.LNX.4.64.0804231202250.15173@schroedinger.engr.sgi.com>
Date:	Wed, 23 Apr 2008 12:05:01 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Pekka Enberg <penberg@...helsinki.fi>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Zdenek Kabelac <zdenek.kabelac@...il.com>,
	Ingo Molnar <mingo@...e.hu>, Jiri Slaby <jirislaby@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, paulmck@...ux.vnet.ibm.com,
	David Miller <davem@...emloft.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-ext4@...r.kernel.org, herbert@...dor.apana.org.au
Subject: Re: 2.6.25-git2: BUG: unable to handle kernel paging request at
 ffffffffffffffff

On Wed, 23 Apr 2008, Pekka Enberg wrote:

>     fault = check_bytes(start + length, POISON_INUSE, remainder);

fault == NULL if the check was successful. Otherwise it contains the first
address that does not match our expectations.

>     if (!fault)
>             return 1;
>     while (end > fault && end[-1] == POISON_INUSE)
>             end--;
> 
>     slab_err(s, page, "Padding overwritten. 0x%p-0x%p", fault, end - 1);
> 
> So how come we're printing out 'fault' as zero and 'end' at 4 GB? Christoph?

We should have returned from the function and not printed this message. If 
we somehow skipped the test for !fault then end could have wrapped around 
which gets us to 4GB.


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