linux-kernel - intel_cacheinfo: potential NULL dereference?

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Message-ID: <4C209C15.9090604@gmail.com>
Date:	Tue, 22 Jun 2010 13:18:45 +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: intel_cacheinfo: potential NULL dereference?

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?

thanks,
--
js
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