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

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Message-ID: <57544d01-a7c6-1ea6-d408-ffe1678e0b5e@quicinc.com>
Date: Thu, 7 Nov 2024 18:32:33 +0530
From: Vikash Garodia <quic_vgarodia@...cinc.com>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Dmitry Baryshkov
	<dmitry.baryshkov@...aro.org>
CC: Stanimir Varbanov <stanimir.k.varbanov@...il.com>,
        Mauro Carvalho Chehab
	<mchehab@...nel.org>,
        <linux-media@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH 1/4] media: venus: hfi_parser: add check to avoid out of
 bound access


On 11/7/2024 5:37 PM, Bryan O'Donoghue wrote:
> On 07/11/2024 10:41, Dmitry Baryshkov wrote:
>>> init_codecs() parses the payload received from firmware and . I don't think we
>>> can control this part when we have something like this from a malicious firmware
>>> payload
>>> HFI_PROPERTY_PARAM_CODEC_SUPPORTED
>>> HFI_PROPERTY_PARAM_CODEC_SUPPORTED
>>> HFI_PROPERTY_PARAM_CODEC_SUPPORTED
>>> ...
>>> Limiting it to second iteration would restrict the functionality when property
>>> HFI_PROPERTY_PARAM_CODEC_SUPPORTED is sent for supported number of codecs.
>> If you can have a malicious firmware (which is owned and signed by
>> Qualcomm / OEM), then you have to be careful and skip duplicates. So
>> instead of just adding new cap to core->caps, you have to go through
>> that array, check that you are not adding a duplicate (and report a
>> [Firmware Bug] for duplicates), check that there is an empty slot, etc.
>>
>> Just ignoring the "extra" entries is not enough.
Thinking of something like this

for_each_set_bit(bit, &core->dec_codecs, MAX_CODEC_NUM) {
    if (core->codecs_count >= MAX_CODEC_NUM)
        return;
    cap = &caps[core->codecs_count++];
    if (cap->codec == BIT(bit)) --> each code would have unique bitfield
        return;
> +1
> 
> This is a more rational argument. If you get a second message, you should surely
> reinit the whole array i.e. update the array with the new list, as opposed to
> throwing away the second message because it over-indexes your local storage..
That would be incorrect to overwrite the array with new list, whenever new
payload is received.

Regards,
Vikash