[FFmpeg-devel] ADPCM task (was Re: files in incoming)

[Stefan Gehrer]

Hi Reimar,

Reimar D?ffinger wrote:
> On Fri, Jan 30, 2009 at 08:06:04AM +0100, Stefan Gehrer wrote:
>> @@ -1303,6 +1304,7 @@
>>              srcC  = src + (avctx->channels-channel) * 4;
>>              srcC += (big_endian ? bytestream_get_be32(&src)
>>                                  : bytestream_get_le32(&src));
>> +            if ((srcC > src_end - 4) || (srcC < src)) break;
> 
> Unfortunately no, a C compiler is allowed to assume that pointer
> operations will never overflow, thus removing the (srcC < src) check.

Interesting. Do you have a source where I can read that up?
And if the answer is ANSI C / ISO 9899, maybe a more specific hint?

> That's why the offset variable in the previous patch would have been a
> good idea, with
> int offset = (big_endian ? bytestream_get_be32(&src)
>                                   : bytestream_get_le32(&src)) +
> 				  (avctx->channels-channel) * 4;
> you could have checked (offset < 0 || offset >= src_end - src - 4)
> That is the best idea I had so far.
> If there is the slightest reason to assume that offset can be > 2GB a
> different check might make sense.

Assuming there is no such reason, attached is your suggestion as a patch.

Stefan
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