linux-kernel - Re: perf,arm -- another (different) fuzzer oops

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Date:	Thu, 8 Aug 2013 13:09:39 +0100
From:	Will Deacon <will.deacon@....com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Vince Weaver <vincent.weaver@...ne.edu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mark Rutland <Mark.Rutland@....com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	"trinity@...r.kernel.org" <trinity@...r.kernel.org>
Subject: Re: perf,arm -- another (different) fuzzer oops

On Thu, Aug 08, 2013 at 12:18:08AM +0100, Stephen Boyd wrote:
> Is config some really big value? It looks like config (or more
> specifically event->attr.config) is ecececec which is larger than 9
> (PERF_COUNT_HW_MAX). I'm fairly certain r4 is event->attr.type
> (PERF_TYPE_HARDWARE) and so we're out of bounds on that array access in
> armpmu_map_hw_event(). Does the below patch fix that?
> 
> ---8<----
> 
> diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
> index d9f5cd4..21f7790 100644
> --- a/arch/arm/kernel/perf_event.c
> +++ b/arch/arm/kernel/perf_event.c
> @@ -53,7 +53,12 @@ armpmu_map_cache_event(const unsigned (*cache_map)
>  static int
>  armpmu_map_hw_event(const unsigned (*event_map)[PERF_COUNT_HW_MAX], u64 config)
>  {
> -       int mapping = (*event_map)[config];
> +       int mapping;
> +
> +       if (config >= PERF_COUNT_HW_MAX)
> +               return -ENOENT;
> +
> +       mapping = (*event_map)[config];

Well spotted, thanks. If you make that return -EINVAL instead of -ENOENT (to
match what we do for cache events) then:

  Acked-by: Will Deacon <will.deacon@....com>

Could you stick it in the patch system please?

Thanks Stephen,

Will
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