linux-kernel - Re: [PATCH 2/3] drivers/perf: arm_pmu: Defer the setting of __oprofile_cpu

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Message-ID: <20160531162834.GR24936@arm.com>
Date:	Tue, 31 May 2016 17:28:34 +0100
From:	Will Deacon <will.deacon@....com>
To:	Julien Grall <julien.grall@....com>
Cc:	mark.rutland@....com, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/3] drivers/perf: arm_pmu: Defer the setting of
 __oprofile_cpu_pmu

On Tue, May 31, 2016 at 12:41:22PM +0100, Julien Grall wrote:
> The global variable __oprofile_cpu_pmu is set before the PMU is fully
> initialized. If an error occurs before the end of the initialization,
> the PMU will be freed and the variable will contain an invalid pointer.
> 
> This will result in a kernel crash when perf will be used.
> 
> Fix it by moving the setting of __oprofile_cpu_pmu when the PMU is fully
> initialized (i.e when it is no longer possible to fail).
> 
> Signed-off-by: Julien Grall <julien.grall@....com>
> Acked-by: Mark Rutland <mark.rutland@....com>
> ---
>  drivers/perf/arm_pmu.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)

Should this one go to -stable too?

Will

> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
> index 6401f0c..95614d2 100644
> --- a/drivers/perf/arm_pmu.c
> +++ b/drivers/perf/arm_pmu.c
> @@ -992,9 +992,6 @@ int arm_pmu_device_probe(struct platform_device *pdev,
>  
>  	armpmu_init(pmu);
>  
> -	if (!__oprofile_cpu_pmu)
> -		__oprofile_cpu_pmu = pmu;
> -
>  	pmu->plat_device = pdev;
>  
>  	if (node && (of_id = of_match_node(of_table, pdev->dev.of_node))) {
> @@ -1030,6 +1027,9 @@ int arm_pmu_device_probe(struct platform_device *pdev,
>  	if (ret)
>  		goto out_destroy;
>  
> +	if (!__oprofile_cpu_pmu)
> +		__oprofile_cpu_pmu = pmu;
> +
>  	pr_info("enabled with %s PMU driver, %d counters available\n",
>  			pmu->name, pmu->num_events);
>  
> -- 
> 1.9.1
>