[FFmpeg-devel] [PATCH 2/5] avcodec/xpmdec: Check size before allocation to avoid truncation

[Michael Niedermayer]

On Fri, Jan 13, 2023 at 05:53:20PM -0300, James Almer wrote:
> On 1/13/2023 5:49 PM, Michael Niedermayer wrote:
> > On Thu, Jan 12, 2023 at 09:11:35PM -0300, James Almer wrote:
> > > 
> > > 
> > > On 1/12/2023 9:01 PM, Michael Niedermayer wrote:
> > > > Fixes:OOM
> > > > Fixes:out of array access (no testcase)
> > > > Fixes: 48567/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_XPM_fuzzer-6573323838685184
> > > > 
> > > > 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/xpmdec.c | 3 +++
> > > >    1 file changed, 3 insertions(+)
> > > > 
> > > > diff --git a/libavcodec/xpmdec.c b/libavcodec/xpmdec.c
> > > > index ff1f51dd32..504cc47d8f 100644
> > > > --- a/libavcodec/xpmdec.c
> > > > +++ b/libavcodec/xpmdec.c
> > > > @@ -356,6 +356,9 @@ static int xpm_decode_frame(AVCodecContext *avctx, AVFrame *p,
> > > >        size *= 4;
> > > > +    if (size > SIZE_MAX)
> > > > +        return AVERROR(ENOMEM);
> > > 
> > > Maybe check for (size > SIZE_MAX / 4) before the multiplication above
> > > instead.
> > 
> > what is the advantage of this ?
> 
> An int64_t value will never be bigger than or equal to SIZE_MAX on 64 bits
> targets, so maybe some compiler out there will warn about it.

hmm ok, ill apply it with that change

thx

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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