linux-kernel - Re: 2.6.28-rc6-git1 -- BUG: unable to handle kernel paging request at ffff8800be8b0019

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Message-Id: <1227859011.6039.2.camel@penberg-laptop>
Date:	Fri, 28 Nov 2008 09:56:50 +0200
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Miles Lane <miles.lane@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, Tejun Heo <htejun@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: 2.6.28-rc6-git1 -- BUG: unable to handle kernel paging request
	at ffff8800be8b0019

On Thu, 2008-11-27 at 17:34 +0000, Hugh Dickins wrote:
> An alternative quick just-for-now fix might be to remove that
> 	namebuf[KSYM_NAME_LEN - 1] = 0;
> from kallsyms_lookup(): as I understand it (please check), that
> could only make sense in cases where the symbol is KSYM_NAME_LEN
> long or longer - in which case, all of the places fixed in the
> patch below would be causing corruption already, even without my
> patch.  I think.  Maybe that "= 0" even serves no purpose at all?

I looked into this and unfortunately that won't help us. For example,
module_address_lookup() will copy KSYM_NAME_LEN - 1 bytes to namebuf
anyway so we'll overflow the buffer.

It would probably be a good idea to add a comment to kallsyms_lookup()
stating that namebuf needs to have at least KSYM_NAME_LEN bytes
available.

		Pekka

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