Re: [PATCH] drm/i915/vrr: require valid min/max vfreq for VRR

[Jani Nikula <jani.nikula@intel.com>]

On Fri, 26 Jun 2026, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> On Thu, Jun 25, 2026 at 04:10:40PM +0300, Jani Nikula wrote:
>> Ensure the EDID provided min/max vfreq are valid. Most scenarios are
>> already covered (by coincidence) through the checks in
>> intel_vrr_is_capable() and intel_vrr_is_in_range(), but be more explicit
>> about it. At worst, a zero min_vfreq could lead to a division by zero in
>> intel_vrr_compute_vmax().
>> 
>> Discovered using AI-assisted static analysis confirmed by Intel Product
>> Security.
>> 
>> Reported-by: Martin Hodo <martin.hodo@intel.com>
>> Fixes: 117cd09ba528 ("drm/i915/display/dp: Compute VRR state in atomic_check")
>> Cc: <stable@vger.kernel.org> # v5.12+
>> Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_vrr.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>> 
>> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
>> index 5d9b11185296..bffbdee76ee1 100644
>> --- a/drivers/gpu/drm/i915/display/intel_vrr.c
>> +++ b/drivers/gpu/drm/i915/display/intel_vrr.c
>> @@ -76,6 +76,10 @@ bool intel_vrr_is_capable(struct intel_connector *connector)
>>  		return false;
>>  	}
>>  
>> +	if (!info->monitor_range.min_vfreq || !info->monitor_range.max_vfreq ||
>> +	    info->monitor_range.min_vfreq > info->monitor_range.max_vfreq)
>> +		return false;
>
> Perhaps it should be the responsibility of the EDID parser to make sure
> the range isn't completely insane?

The min_vfreq/max_vfreq may be 0 if the EDID doesn't have the info, and
if the EDID has bogus info, leaving them to 0 is pretty much the only
thing we can do.

Since we need the !0 check here anyway, I decided to start off with
this.

BR,
Jani.

>
>> +
>>  	return info->monitor_range.max_vfreq - info->monitor_range.min_vfreq > 10;
>
> I've been tempted to get rid of this completely arbitrary 10Hz thing as well.
>
>>  }
>>  
>> -- 
>> 2.47.3

-- 
Jani Nikula, Intel