[FFmpeg-devel] [PATCH 5/5] avcodec/apedec: Check max_samples

[James Almer]

On 9/3/2019 8:13 AM, Michael Niedermayer wrote:
> On Mon, Sep 02, 2019 at 09:40:47PM -0300, James Almer wrote:
>> On 9/2/2019 9:14 PM, Michael Niedermayer wrote:
>>> Fixes: OOM
>>> Fixes: 16627/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_APE_fuzzer-5638059583864832
>>>
>>> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
>>> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
>>> ---
>>>  libavcodec/apedec.c | 3 +++
>>>  1 file changed, 3 insertions(+)
>>>
>>> diff --git a/libavcodec/apedec.c b/libavcodec/apedec.c
>>> index e218f7c043..774ce18531 100644
>>> --- a/libavcodec/apedec.c
>>> +++ b/libavcodec/apedec.c
>>> @@ -1475,6 +1475,9 @@ static int ape_decode_frame(AVCodecContext *avctx, void *data,
>>>              return AVERROR_INVALIDDATA;
>>>          }
>>>  
>>> +        if (nblocks * (int64_t)avctx->channels > avctx->max_samples)
>>> +            return AVERROR(EINVAL);
>>> +
>>
>> Shouldn't this be checked in ff_get_buffer()? Same as max_pixels, but
>> checking "frame->nb_samples > avctx->max_samples" instead or
>> width/height. Otherwise it will barely be used.
> 
> you are correct, it should be checked in *get_buffer somewhere too.
> But the offending allocation occurs before any *get_buffer calls so
> this check here is what is neccessary and sufficient for this specific
> bug

If the allocation you're talking about is
https://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavcodec/apedec.c;h=490b11b94e0b1666f18248b2b247c874fed6e0bc;hb=HEAD#l1500
then you could just move it (and the five lines that follow it) right
below the ff_get_buffer() call.

But it should be ok either way.

> 
> Thanks
> 
> [...]
> 
> 
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