linux-kernel - Re: [kvm-unit-tests Patch v3 03/11] x86: pmu: Add asserts to warn inconsistent fixed events and counters

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Date: Wed, 27 Mar 2024 05:30:12 +0000
From: Mingwei Zhang <mizhang@...gle.com>
To: Dapeng Mi <dapeng1.mi@...ux.intel.com>
Cc: Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Zhenyu Wang <zhenyuw@...ux.intel.com>,
	Zhang Xiong <xiong.y.zhang@...el.com>,
	Like Xu <like.xu.linux@...il.com>,
	Jinrong Liang <cloudliang@...cent.com>,
	Dapeng Mi <dapeng1.mi@...el.com>
Subject: Re: [kvm-unit-tests Patch v3 03/11] x86: pmu: Add asserts to warn
 inconsistent fixed events and counters

On Wed, Jan 03, 2024, Dapeng Mi wrote:
> Current PMU code deosn't check whether PMU fixed counter number is
> larger than pre-defined fixed events. If so, it would cause memory
> access out of range.
> 
> So add assert to warn this invalid case.
> 
> Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
Reviewed-by: Mingwei Zhang <mizhang@...gle.com>
> ---
>  x86/pmu.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/x86/pmu.c b/x86/pmu.c
> index a13b8a8398c6..a42fff8d8b36 100644
> --- a/x86/pmu.c
> +++ b/x86/pmu.c
> @@ -111,8 +111,12 @@ static struct pmu_event* get_counter_event(pmu_counter_t *cnt)
>  		for (i = 0; i < gp_events_size; i++)
>  			if (gp_events[i].unit_sel == (cnt->config & 0xffff))
>  				return &gp_events[i];
> -	} else
> -		return &fixed_events[cnt->ctr - MSR_CORE_PERF_FIXED_CTR0];
> +	} else {
> +		int idx = cnt->ctr - MSR_CORE_PERF_FIXED_CTR0;
maybe unsigned int is better?
> +
> +		assert(idx < ARRAY_SIZE(fixed_events));
> +		return &fixed_events[idx];
> +	}
>  
>  	return (void*)0;
>  }
> @@ -245,6 +249,7 @@ static void check_fixed_counters(void)
>  	};
>  	int i;
>  
> +	assert(pmu.nr_fixed_counters <= ARRAY_SIZE(fixed_events));
>  	for (i = 0; i < pmu.nr_fixed_counters; i++) {
>  		cnt.ctr = fixed_events[i].unit_sel;
>  		measure_one(&cnt);
> @@ -266,6 +271,7 @@ static void check_counters_many(void)
>  			gp_events[i % gp_events_size].unit_sel;
>  		n++;
>  	}
> +	assert(pmu.nr_fixed_counters <= ARRAY_SIZE(fixed_events));
>  	for (i = 0; i < pmu.nr_fixed_counters; i++) {
>  		cnt[n].ctr = fixed_events[i].unit_sel;
>  		cnt[n].config = EVNTSEL_OS | EVNTSEL_USR;
> -- 
> 2.34.1
>