Re: [PATCH v2] drm/i915/edp: Check supported link rates DPCD read

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

On Fri, 29 May 2026, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Fri, 29 May 2026, Nikita Zhandarovich <n.zhandarovich@fintech.ru> wrote:
>> intel_edp_set_sink_rates() reads DP_SUPPORTED_LINK_RATES into a local
>> stack array and then parses the array unconditionally. If the read
>> fails, the array contents are not valid and may result in bogus sink
>> link rates being used.
>>
>> Use drm_dp_dpcd_read_data() and clear the sink rate array on failure,
>> so the existing parser falls back to the default sink rate handling.
>>
>> Found by Linux Verification Center (linuxtesting.org) with static
>> analysis tool SVACE.
>>
>> Fixes: 68f357cb7347 ("drm/i915/dp: generate and cache sink rate array for all DP, not just eDP 1.4")
>> Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
>
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>

And pushed to drm-intel-next, thanks for the patch.

>
>> ---
>> v1 -> v2:
>> - Use drm_dp_dpcd_read_data() instead of drm_dp_dpcd_read().
>> - Avoid the goto by clearing sink_rates on read failure, as suggested by
>>   Jani Nikula.
>> - Adjust patch description.
>>
>>  drivers/gpu/drm/i915/display/intel_dp.c | 11 +++++++++--
>>  1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index 6ef2a0043cda..5c3e816b0135 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -4678,10 +4678,17 @@ intel_edp_set_sink_rates(struct intel_dp *intel_dp)
>>  
>>  	if (intel_dp->edp_dpcd[0] >= DP_EDP_14) {
>>  		__le16 sink_rates[DP_MAX_SUPPORTED_RATES];
>> +		int ret;
>>  		int i;
>>  
>> -		drm_dp_dpcd_read(&intel_dp->aux, DP_SUPPORTED_LINK_RATES,
>> -				 sink_rates, sizeof(sink_rates));
>> +		ret = drm_dp_dpcd_read_data(&intel_dp->aux,
>> +					    DP_SUPPORTED_LINK_RATES,
>> +					    sink_rates, sizeof(sink_rates));
>> +		if (ret < 0) {
>> +			drm_dbg_kms(display->drm,
>> +				    "Unable to read eDP supported link rates, using default rates\n");
>> +			memset(sink_rates, 0, sizeof(sink_rates));
>> +		}
>>  
>>  		for (i = 0; i < ARRAY_SIZE(sink_rates); i++) {
>>  			int rate;

-- 
Jani Nikula, Intel