linux-kernel - Re: [PATCH v2 1/4] venus: hfi: add checks to perform sanity on queue pointers

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Date:   Fri, 11 Aug 2023 11:16:00 +0530
From:   Vikash Garodia <quic_vgarodia@...cinc.com>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        <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 1/4] venus: hfi: add checks to perform sanity on queue
 pointers


On 8/10/2023 4:54 PM, Bryan O'Donoghue wrote:
> On 10/08/2023 03:25, Vikash Garodia wrote:
>> Read and write pointers are used to track the packet index in the memory
>> shared between video driver and firmware. There is a possibility of OOB
>> access if the read or write pointer goes beyond the queue memory size.
>> Add checks for the read and write pointer to avoid OOB access.
>>
>> Cc: stable@...r.kernel.org
>> Fixes: d96d3f30c0f2 ("[media] media: venus: hfi: add Venus HFI files")
>> Signed-off-by: Vikash Garodia <quic_vgarodia@...cinc.com>
>> ---
>>   drivers/media/platform/qcom/venus/hfi_venus.c | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/media/platform/qcom/venus/hfi_venus.c
>> b/drivers/media/platform/qcom/venus/hfi_venus.c
>> index f0b4638..4ddabb1 100644
>> --- a/drivers/media/platform/qcom/venus/hfi_venus.c
>> +++ b/drivers/media/platform/qcom/venus/hfi_venus.c
>> @@ -206,6 +206,11 @@ static int venus_write_queue(struct venus_hfi_device *hdev,
>>         new_wr_idx = wr_idx + dwords;
>>       wr_ptr = (u32 *)(queue->qmem.kva + (wr_idx << 2));
>> +
>> +    if (wr_ptr < (u32 *)queue->qmem.kva ||
>> +        wr_ptr > (u32 *)(queue->qmem.kva + queue->qmem.size - sizeof(*wr_ptr)))
>> +        return -EINVAL;
>> +
>>       if (new_wr_idx < qsize) {
>>           memcpy(wr_ptr, packet, dwords << 2);
>>       } else {
>> @@ -273,6 +278,11 @@ static int venus_read_queue(struct venus_hfi_device *hdev,
>>       }
>>         rd_ptr = (u32 *)(queue->qmem.kva + (rd_idx << 2));
>> +
>> +    if (rd_ptr < (u32 *)queue->qmem.kva ||
>> +        rd_ptr > (u32 *)(queue->qmem.kva + queue->qmem.size - sizeof(*rd_ptr)))
>> +        return -EINVAL;
>> +
>>       dwords = *rd_ptr >> 2;
>>       if (!dwords)
>>           return -EINVAL;
> 
> What is the bit-shifting for ?
If the query is related to dwords, the bit shift is to convert the size of
packet in words.

Regards,
Vikash