linux-kernel - Re: [PATCH] cpufreq: intel_pstate: fix possible integer overflow

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Message-ID: <52654EA6.6020805@gmail.com>
Date:	Mon, 21 Oct 2013 08:56:22 -0700
From:	Dirk Brandewie <dirk.brandewie@...il.com>
To:	"Geyslan G. Bem" <geyslan@...il.com>, kernel-br@...glegroups.com
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	"open list:CPU FREQUENCY DRI..." <cpufreq@...r.kernel.org>,
	"open list:CPU FREQUENCY DRI..." <linux-pm@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: intel_pstate: fix possible integer overflow

On 10/19/2013 08:31 PM, Geyslan G. Bem wrote:
> The expression 'pstate << 8' is evaluated using 32-bit arithmetic while
> 'val' expects an expression of type u64.
>
> Signed-off-by: Geyslan G. Bem <geyslan@...il.com>
Acked-by: Dirk Brandewie <dirk.j.brandewie@...el.com>
> ---
>   drivers/cpufreq/intel_pstate.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index badf620..43446b5 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -395,7 +395,7 @@ static void intel_pstate_set_pstate(struct cpudata *cpu, int pstate)
>   	trace_cpu_frequency(pstate * 100000, cpu->cpu);
>
>   	cpu->pstate.current_pstate = pstate;
> -	val = pstate << 8;
> +	val = (u64)pstate << 8;
>   	if (limits.no_turbo)
>   		val |= (u64)1 << 32;
>
>

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