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Date: Mon, 14 Jan 2013 17:23:46 +0000
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Cong Ding <dinggnu@gmail.com>
Cc: Will Deacon <will.deacon@arm.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm: kernel/perf_event_cpu.c: fix error null pointer
	dereference check
Message-ID: <20130114172346.GK23505@n2100.arm.linux.org.uk>
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On Mon, Jan 14, 2013 at 05:18:53PM +0000, Cong Ding wrote:
> the pointer cpu_pmu is used without null pointer dereference check, and is
> checked after the using of it, so we move the null pointer check to before the
> first use.

The NULL pointer check is not necessary.  cpu_pmu_init() is called
after cpu_pmu has already been dereferenced by its caller:

        cpu_pmu = pmu;
        cpu_pmu->plat_device = pdev;
        cpu_pmu_init(cpu_pmu);

So...

> -	/* Ensure the PMU has sane values out of reset. */
> -	if (cpu_pmu && cpu_pmu->reset)

Just replace this with:
	if (cpu_pmu->reset)