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Subject: Re: [PATCH V2 3/3] perf/x86/intel/uncore: Validate MMIO address
 before accessing
To:     Andi Kleen <ak@linux.intel.com>
Cc:     peterz@infradead.org, mingo@redhat.com,
        linux-kernel@vger.kernel.org, David.Laight@aculab.com
References: <1590671727-99311-1-git-send-email-kan.liang@linux.intel.com>
 <1590671727-99311-3-git-send-email-kan.liang@linux.intel.com>
 <20200528133008.GH611145@tassilo.jf.intel.com>
From:   "Liang, Kan" <kan.liang@linux.intel.com>
Message-ID: <4f804e10-97c0-9861-4131-b33ca977d2eb@linux.intel.com>
Date:   Thu, 28 May 2020 09:46:42 -0400
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On 5/28/2020 9:30 AM, Andi Kleen wrote:
> On Thu, May 28, 2020 at 06:15:27AM -0700, kan.liang@linux.intel.com wrote:
>> From: Kan Liang <kan.liang@linux.intel.com>
>>
>> An oops will be triggered, if perf tries to access an invalid address
>> which exceeds the mapped area.
>>
>> Check the address before the actual access to MMIO sapce of an uncore
>> unit.
> 
> Ah ok the range check is here
> 
>>
>> Suggested-by: David Laight <David.Laight@ACULAB.COM>
>> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
>> ---
>>   arch/x86/events/intel/uncore.c       |  3 +++
>>   arch/x86/events/intel/uncore.h       | 12 ++++++++++++
>>   arch/x86/events/intel/uncore_snbep.c |  6 ++++++
>>   3 files changed, 21 insertions(+)
>>
>> diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
>> index cf76d66..284f8e7 100644
>> --- a/arch/x86/events/intel/uncore.c
>> +++ b/arch/x86/events/intel/uncore.c
>> @@ -132,6 +132,9 @@ u64 uncore_mmio_read_counter(struct intel_uncore_box *box,
>>   	if (!box->io_addr)
>>   		return 0;
>>   
>> +	if (!is_valid_mmio_offset(box, event->hw.event_base))
>> +		return 0;
> 
> Is this function used somewhere else? Otherwise it should be added
> together with its users.
> 

Yes, it's generic function. Current MMIO uncore units invoke it to read 
counter.

Thanks,
Kan