[FFmpeg-devel] [PATCH] Fix potential av_find_opt() crash if context is NULL

[Michael Niedermayer]

On Thu, Oct 30, 2008 at 12:14:36AM +0100, Stefano Sabatini wrote:
> On date Wednesday 2008-10-29 00:43:16 +0100, Michael Niedermayer encoded:
> > On Wed, Oct 29, 2008 at 12:27:35AM +0100, Stefano Sabatini wrote:
> > > Hi, as in patch.
> > > 
> > > This happens for example in libavfilter-soc with:
> > > ffplay -foo x
> > > 
> > > when --enable-avfilter, in this case sws_opts is NULL.
> > 
> > could you elaborate a little more how above is causing a NULL
> > to be passed.
> > All readers surely could guess but i think it would improve the
> > responses if everyone would know what happens where 
> 
> We have:
> 
> #if !ENABLE_AVFILTER
>     sws_opts = sws_getContext(16,16,0, 16,16,0, sws_flags, NULL,NULL,NULL);
> #endif
> 
> So sws_opts is not initialized and is NULL.
> 
> Then when an unknown option is parsed and processed in opt_default we
> have:
> 
>     if(!o)
>         o = av_set_string2(sws_opts, opt, arg, 1);
> 
> which calls av_find_opt() and crashes.
> 
> Optionally we could specify in the doc the condition for which
> opt_find_opt has to take always a non-NULL value as obj, but I think
> it is more robust and semnatically more correct to simply return NULL
> in case of a NULL obj.

bleh ...
the problem is obvious in the ENABLE_AVFILTER #ifdefs
if sws is not used by ffmpegm sws_opts itself should not even exist with
avfilter

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you really think that XML is the answer, then you definitly missunderstood
the question -- Attila Kinali
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