Re: [PATCH 1/4] media: venus: hfi_parser: add check to avoid out of bound access

[Vikash Garodia <quic_vgarodia@quicinc.com>]

On 11/5/2024 4:21 PM, Bryan O'Donoghue wrote:
> On 05/11/2024 08:54, Vikash Garodia wrote:
>> There is a possibility that init_codecs is invoked multiple times during
>> manipulated payload from video firmware. In such case, if codecs_count
>> can get incremented to value more than MAX_CODEC_NUM, there can be OOB
>> access. Keep a check for max accessible memory before accessing it.
>>
>> Cc: stable@vger.kernel.org
>> Fixes: 1a73374a04e5 ("media: venus: hfi_parser: add common capability parser")
>> Signed-off-by: Vikash Garodia <quic_vgarodia@quicinc.com>
>> ---
>>   drivers/media/platform/qcom/venus/hfi_parser.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/media/platform/qcom/venus/hfi_parser.c
>> b/drivers/media/platform/qcom/venus/hfi_parser.c
>> index
>> 3df241dc3a118bcdeb2c28a6ffdb907b644d5653..27d0172294d5154f4839e8cef172f9a619dfa305 100644
>> --- a/drivers/media/platform/qcom/venus/hfi_parser.c
>> +++ b/drivers/media/platform/qcom/venus/hfi_parser.c
>> @@ -23,6 +23,8 @@ static void init_codecs(struct venus_core *core)
>>           return;
>>         for_each_set_bit(bit, &core->dec_codecs, MAX_CODEC_NUM) {
>> +        if (core->codecs_count >= MAX_CODEC_NUM)
>> +            return;
>>           cap = &caps[core->codecs_count++];
>>           cap->codec = BIT(bit);
>>           cap->domain = VIDC_SESSION_TYPE_DEC;
>> @@ -30,6 +32,8 @@ static void init_codecs(struct venus_core *core)
>>       }
>>         for_each_set_bit(bit, &core->enc_codecs, MAX_CODEC_NUM) {
>> +        if (core->codecs_count >= MAX_CODEC_NUM)
>> +            return;
>>           cap = &caps[core->codecs_count++];
>>           cap->codec = BIT(bit);
>>           cap->domain = VIDC_SESSION_TYPE_ENC;
>>
> 
> I don't see how codecs_count could be greater than the control, since you
> increment by one on each loop but >= is fine too I suppose.
Assume the payload from malicious firmware is packed like below
HFI_PROPERTY_PARAM_CODEC_SUPPORTED
HFI_PROPERTY_PARAM_CODEC_SUPPORTED
HFI_PROPERTY_PARAM_CODEC_SUPPORTED
.....
for 32 or more instances of above type

Regards,
Vikash
> 
> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>