[FFmpeg-devel] [PATCH 3/7] avcodec/alsdec: Fix integer overflow with buffer number

[Thilo Borgmann]

Am 06.07.19 um 22:10 schrieb Michael Niedermayer:
> On Sat, Jul 06, 2019 at 09:39:32PM +0200, Thilo Borgmann wrote:
>> Am 21.06.19 um 09:00 schrieb Reimar Döffinger:
>>>
>>>
>>> On 21.06.2019, at 00:47, Michael Niedermayer <michael at niedermayer.cc> wrote:
>>>
>>>> Fixes: signed integer overflow: 65313 * 65313 cannot be represented in type 'int'
>>>> Fixes: 15290/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-5738074249625600
>>>>
>>>> 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/alsdec.c | 2 ++
>>>> 1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
>>>> index 79d22b7c2b..8e0d3e5f83 100644
>>>> --- a/libavcodec/alsdec.c
>>>> +++ b/libavcodec/alsdec.c
>>>> @@ -1990,6 +1990,8 @@ static av_cold int decode_init(AVCodecContext *avctx)
>>>>
>>>>     // allocate quantized parcor coefficient buffer
>>>>     num_buffers = sconf->mc_coding ? avctx->channels : 1;
>>>> +    if (num_buffers * (uint64_t)num_buffers > INT_MAX)
>>>> +        return AVERROR_INVALIDDATA;
>>>
>>> It would be nice if it was clear which code this check protects, i.e. some connection between the check and the code that overflows.
>>> I guess one might also ask if > 30 000 channels might not be something to catch and disallow earlier and generally...
>>
>> AFAICT the specs allow all 16 bit aka 65536 (+1) channels. For the case that remark from Raimar had been addressed..
> 
> its the chan_data_buffer allocation. Ill add a comment
> 
> 
>>
>> The rest lgtm. I would appreciate s.o. bumping me if I miss something about ALS on devel, pls 0:-)
> 
> not sure i understand the abbreviation but i will apply the patchset as it
> seems, thats the consensus and ill try to ping you in the future of als patches unless
> i forget ... sadly i tend to forget these things ...

"Someone".

Do apply. The rest is just in regard of redundance, I'll not miss every patch ^^

Thanks,
Thilo