linux-kernel - Re: v2.6.26-rc7: BUG: unable to handle kernel NULL pointer dereference

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Message-ID: <485FD644.80208@sgi.com>
Date:	Mon, 23 Jun 2008 09:58:44 -0700
From:	Mike Travis <travis@....com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Vegard Nossum <vegard.nossum@...il.com>,
	Adrian Bunk <bunk@...nel.org>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	linux-kernel@...r.kernel.org, Gautham R Shenoy <ego@...ibm.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Zhang, Yanmin" <yanmin.zhang@...el.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: v2.6.26-rc7: BUG: unable to handle kernel NULL pointer dereference

Rusty Russell wrote:
> On Monday 23 June 2008 02:29:07 Vegard Nossum wrote:
>> And the (cpu < nr_cpu_ids) fails because the CPU has just been
>> offlined (or failed to initialize, but it's the same thing), while
>> NR_CPUS is the value that was compiled in as CONFIG_NR_CPUS (so the
>> former check will always be true).
>>
>> I don't think it is valid to ask for a per_cpu() variable on a CPU
>> which does not exist, though
> 
> Yes it is.  As long as cpu_possible(cpu), per_cpu(cpu) is valid.
> 
> The number check should be removed: checking cpu_possible() is sufficient.
> 
> Hope that helps,
> Rusty.

I don't see a check for index being out of range in cpu_possible().

Thanks,
Mike
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