linux-kernel - [PATCH] arm: kernel/perf_event_cpu.c: fix error null pointer dereference check

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Date:	Mon, 14 Jan 2013 17:18:53 +0000
From:	Cong Ding <dinggnu@...il.com>
To:	Will Deacon <will.deacon@....com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Russell King <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:	Cong Ding <dinggnu@...il.com>
Subject: [PATCH] arm: kernel/perf_event_cpu.c: fix error null pointer dereference check

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.

Signed-off-by: Cong Ding <dinggnu@...il.com>
---
 arch/arm/kernel/perf_event_cpu.c |   14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/arm/kernel/perf_event_cpu.c b/arch/arm/kernel/perf_event_cpu.c
index efa5295..16aa979 100644
--- a/arch/arm/kernel/perf_event_cpu.c
+++ b/arch/arm/kernel/perf_event_cpu.c
@@ -142,13 +142,15 @@ static void cpu_pmu_init(struct arm_pmu *cpu_pmu)
 		raw_spin_lock_init(&events->pmu_lock);
 	}
 
-	cpu_pmu->get_hw_events	= cpu_pmu_get_cpu_events;
-	cpu_pmu->request_irq	= cpu_pmu_request_irq;
-	cpu_pmu->free_irq	= cpu_pmu_free_irq;
+	if (cpu_pmu) {
+		cpu_pmu->get_hw_events	= cpu_pmu_get_cpu_events;
+		cpu_pmu->request_irq	= cpu_pmu_request_irq;
+		cpu_pmu->free_irq	= cpu_pmu_free_irq;
 
-	/* Ensure the PMU has sane values out of reset. */
-	if (cpu_pmu && cpu_pmu->reset)
-		on_each_cpu(cpu_pmu->reset, cpu_pmu, 1);
+		/* Ensure the PMU has sane values out of reset. */
+		if (cpu_pmu->reset)
+			on_each_cpu(cpu_pmu->reset, cpu_pmu, 1);
+	}
 }
 
 /*
-- 
1.7.9.5

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