linux-kernel - Re: intel_cacheinfo: potential NULL dereference?

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Date:	Tue, 22 Jun 2010 13:20:14 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	borislav.petkov@....com
CC:	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: intel_cacheinfo: potential NULL dereference?

On 06/22/2010 01:18 PM, Jiri Slaby wrote:
> Hi,
> 
> commit 9350f982 changed the code so it looks like:
> static ssize_t store_cache_disable(struct _cpuid4_info *this_leaf,
>                                    const char *buf, size_t count,
>                                    unsigned int slot)
> {
>         struct pci_dev *dev = this_leaf->l3->dev;   <<1>>
>         int cpu = cpumask_first(to_cpumask(this_leaf->shared_cpu_map));
>         unsigned long val = 0;
> 
> #define SUBCACHE_MASK   (3UL << 20)
> #define SUBCACHE_INDEX  0xfff
> 
>         if (!this_leaf->l3 || !this_leaf->l3->can_disable)  <<2>>
>                 return -EINVAL;
> 
> Stanse found, that this_leaf->l3 is dereferenced at <<1>>, but checked
> for being NULL at <<2>>. Is the check superfluous or the dev assignment
> should go after the check?

Oh, and I have another report with same symptoms for show_cache_disable.

-- 
js
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