Re: [FFmpeg-devel] [PATCH 1/5] avcodec/bsf/(hevc|vvc)_mp4toannexb: Ensure extradata_size < INT_MAX

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

James Almer:
> On 2/17/2024 11:41 PM, Andreas Rheinhardt wrote:
>> AVCodecParameters.extradata_size is an int.
>>
>> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
>> ---
>>   libavcodec/bsf/hevc_mp4toannexb.c | 2 +-
>>   libavcodec/bsf/vvc_mp4toannexb.c  | 2 +-
>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/libavcodec/bsf/hevc_mp4toannexb.c
>> b/libavcodec/bsf/hevc_mp4toannexb.c
>> index 8eec18f31e..c0df2b79a6 100644
>> --- a/libavcodec/bsf/hevc_mp4toannexb.c
>> +++ b/libavcodec/bsf/hevc_mp4toannexb.c
>> @@ -69,7 +69,7 @@ static int hevc_extradata_to_annexb(AVBSFContext *ctx)
>>                 if (!nalu_len ||
>>                   nalu_len > bytestream2_get_bytes_left(&gb) ||
>> -                4 + AV_INPUT_BUFFER_PADDING_SIZE + nalu_len >
>> SIZE_MAX - new_extradata_size) {
>> +                4 + nalu_len > FFMIN(INT_MAX, SIZE_MAX) -
>> AV_INPUT_BUFFER_PADDING_SIZE - new_extradata_size) {
>>                   ret = AVERROR_INVALIDDATA;
>>                   goto fail;
>>               }
>> diff --git a/libavcodec/bsf/vvc_mp4toannexb.c
>> b/libavcodec/bsf/vvc_mp4toannexb.c
>> index 36bdae8f49..1b851f3223 100644
>> --- a/libavcodec/bsf/vvc_mp4toannexb.c
>> +++ b/libavcodec/bsf/vvc_mp4toannexb.c
>> @@ -159,7 +159,7 @@ static int vvc_extradata_to_annexb(AVBSFContext *ctx)
>>                 if (!nalu_len ||
>>                   nalu_len > bytestream2_get_bytes_left(&gb) ||
>> -                4 + AV_INPUT_BUFFER_PADDING_SIZE + nalu_len >
>> SIZE_MAX - new_extradata_size) {
>> +                4 + nalu_len > FFMIN(INT_MAX, SIZE_MAX) -
>> AV_INPUT_BUFFER_PADDING_SIZE - new_extradata_size) {
> 
> Just use INT_MAX, there's no point in this check. Do you expect a system
> where an int is smaller than the type meant to store size of buffers in
> memory?
> 

We typically try to avoid such assumptions (although we actually have
lots of INT_MAX <= SIZE_MAX assumptions in the codebase, namely lots of
instances where one uses an int and an allocation function).
In this case using FFMIN(INT_MAX, SIZE_MAX) will make it easier to find
these lines via git grep when extradata_size is switched to size_t.
Alternatively, one could add an AV_CODECPAR_MAX_EXTRADATA_SIZE define,
but this is even longer than FFMIN(INT_MAX, SIZE_MAX).

- Andreas

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