[FFmpeg-devel] [PATCH] avcodec/alsdec: properly allocate raw_buffer

[Paul B Mahol]

On 7/2/17, Thilo Borgmann <thilo.borgmann at mail.de> wrote:
> Am 01.07.17 um 03:38 schrieb Paul B Mahol:
>> This also reverts 18f94df8.
>>
>> Fixes #5297.
>>
>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>> ---
>>  libavcodec/alsdec.c | 7 +------
>>  1 file changed, 1 insertion(+), 6 deletions(-)
>> [...]
>> @@ -2062,7 +2057,7 @@ static av_cold int decode_init(AVCodecContext
>> *avctx)
>>      channel_size      = sconf->frame_length + sconf->max_order;
>>
>>      ctx->prev_raw_samples = av_malloc_array(sconf->max_order,
>> sizeof(*ctx->prev_raw_samples));
>> -    ctx->raw_buffer       = av_mallocz_array(avctx->channels *
>> channel_size, sizeof(*ctx->raw_buffer));
>> +    ctx->raw_buffer       = av_mallocz_array(avctx->channels *
>> channel_size + sconf->max_order, sizeof(*ctx->raw_buffer));
>>      ctx->raw_samples      = av_malloc_array(avctx->channels,
>> sizeof(*ctx->raw_samples));
>
> This looks like guessing only about a needed overhead to the raw buffer.
> What is
> needed and actually done, is an overhead of max_order and that is already
> added
> to the buffer length three lines above the proposed change. So this is
> nothing
> more than guessing an overhead of 2*max_order should be enough but it does
> not
> resolve knowingly any cause of the bug.
>
> Therefore no, this still does not get applied until the actual reason of the
> bug
> is found and properly fixed. I've got less time than I thought today and I
> could
> not dive in as deep as I want. I cannot predict if there will be more time
> for
> me to do it soon. So Paul, I'd appreciate if you could solve this bug but I
> will
> only accept a proper patch and no guesswork.

This is not guesswork, The raw buffers needs this enough bytes.

See this line:
    ctx->raw_samples[0] = ctx->raw_buffer + sconf->max_order;

>
> -Thilo
>
> p.s. I have the original pred.wav used by the ticket author and for me both
> rm22rev2 and rm23 of the reference codec fail to decode pred.mp4 properly.
> Does
> anyone else have the same problem with the reference codecs?

Reference code crashes all the time.