linux-kernel - Re: [PATCH v2 4/4] venus: hfi_parser: Add check to keep the number of codecs within range

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Date:   Fri, 11 Aug 2023 11:41:37 +0100
From:   Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To:     Vikash Garodia <quic_vgarodia@...cinc.com>,
        stanimir.k.varbanov@...il.com, agross@...nel.org,
        andersson@...nel.org, konrad.dybcio@...aro.org, mchehab@...nel.org,
        hans.verkuil@...co.com, tfiga@...omium.org
Cc:     linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2 4/4] venus: hfi_parser: Add check to keep the number of
 codecs within range

On 11/08/2023 09:49, Vikash Garodia wrote:
> 
> On 8/11/2023 2:12 PM, Bryan O'Donoghue wrote:
>> On 11/08/2023 07:04, Vikash Garodia wrote:
>>>
>>> On 8/10/2023 5:03 PM, Bryan O'Donoghue wrote:
>>>> On 10/08/2023 03:25, Vikash Garodia wrote:
>>>>> +    if (hweight_long(core->dec_codecs) + hweight_long(core->enc_codecs) >
>>>>> MAX_CODEC_NUM)
>>>>> +        return;
>>>>> +
>>>>
>>>> Shouldn't this be >= ?
>>> Not needed. Lets take a hypothetical case when core->dec_codecs has initial 16
>>> (0-15) bits set and core->enc_codecs has next 16 bits (16-31) set. The bit count
>>> would be 32. The codec loop after this check would run on caps array index 0-31.
>>> I do not see a possibility for OOB access in this case.
>>>
>>>>
>>>> struct hfi_plat_caps caps[MAX_CODEC_NUM];
>>>>
>>>> ---
>>>> bod
>>>>
>>
>> Are you not doing a general defensive coding pass in this series ie
>>
>> "[PATCH v2 2/4] venus: hfi: fix the check to handle session buffer requirement"
> 
> In "PATCH v2 2/4", there is a possibility if the check does not consider "=".
> Here in this patch, I do not see a possibility.
> 
>>
>> ---
>> bod

But surely hweight_long(core->dec_codecs) + 
hweight_long(core->enc_codecs) == MAX_CODEC_NUM is an invalid offset ?

---
bod