ARM: perf: check that we have a platform device when reserving PMU

Attempting to use a hardware counter on a platform with a supported PMU
but where the platform_device (defining the interrupts) has not been
registered results in a NULL pointer dereference.

This patch fixes the problem by checking that we actually have a platform
device registered before attempting to grab the interrupts.

Reported-by: Pawel Moll <pawel.moll@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index e508066..c475379 100644 (file)
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -402,6 +402,9 @@ armpmu_reserve_hardware(struct arm_pmu *armpmu)
        int i, err, irq, irqs;
        struct platform_device *pmu_device = armpmu->plat_device;
 
+       if (!pmu_device)
+               return -ENODEV;
+
        err = reserve_pmu(armpmu->type);
        if (err) {
                pr_warning("unable to reserve pmu\n");