[FFmpeg-devel] [PATCH] Fix segv when decoding gray8

Michael Niedermayer michaelni
Thu Jun 3 22:48:12 CEST 2010

On Thu, Jun 03, 2010 at 12:11:41PM -0700, Baptiste Coudurier wrote:
> On 06/03/2010 03:36 AM, Michael Niedermayer wrote:
>> On Wed, Jun 02, 2010 at 06:39:26PM -0700, Baptiste Coudurier wrote:
>>> Hi guys,
>>> $subject.
>>> frame->data[1] is set by avpicture_fill which is called with buf passed
>>> from the demuxer.
>>> However, for gray8 the data stored is only width*height, so is too small
>>> for the palette, and will segv, memcpying.
>>> I'm not sure what is the right fix here, buf is supposed to be const.
>> as this case can only arrise from use of deprecated (and buggy) palette
>> passing API, the correct (long term goal) is to change all codecs so they
>> finally stop using this highly unpredictable race condition ridden api.
>> until then, your patch may be ok
> I don't think this is related to the API.
> You cannot generate the palette for gray8 (according to pixfmt.h) _anyway_ 
> since the data buffer is not big enough, since it comes from the demuxer 
> itself.
> So either, the picture needs to be copied and the palette generated, or we 
> skip the palette generation.

maybe iam missing something but why cant  data[1] that contains the palette
point to some pal[256] from the context while data[0] would point to the
buffer that originates from the demuxer?


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Good people do not need laws to tell them to act responsibly, while bad
people will find a way around the laws. -- Plato
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