[FFmpeg-devel] [PATCH 5/5] avcodec/apedec: Check max_samples

[Michael Niedermayer]

On Tue, Sep 03, 2019 at 02:39:27PM -0300, James Almer wrote:
> On 9/3/2019 8:13 AM, Michael Niedermayer wrote:
> > On Mon, Sep 02, 2019 at 09:40:47PM -0300, James Almer wrote:
> >> On 9/2/2019 9:14 PM, Michael Niedermayer wrote:
> >>> Fixes: OOM
> >>> Fixes: 16627/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_APE_fuzzer-5638059583864832
> >>>
> >>> 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/apedec.c | 3 +++
> >>>  1 file changed, 3 insertions(+)
> >>>
> >>> diff --git a/libavcodec/apedec.c b/libavcodec/apedec.c
> >>> index e218f7c043..774ce18531 100644
> >>> --- a/libavcodec/apedec.c
> >>> +++ b/libavcodec/apedec.c
> >>> @@ -1475,6 +1475,9 @@ static int ape_decode_frame(AVCodecContext *avctx, void *data,
> >>>              return AVERROR_INVALIDDATA;
> >>>          }
> >>>  
> >>> +        if (nblocks * (int64_t)avctx->channels > avctx->max_samples)
> >>> +            return AVERROR(EINVAL);
> >>> +
> >>
> >> Shouldn't this be checked in ff_get_buffer()? Same as max_pixels, but
> >> checking "frame->nb_samples > avctx->max_samples" instead or
> >> width/height. Otherwise it will barely be used.
> > 
> > you are correct, it should be checked in *get_buffer somewhere too.
> > But the offending allocation occurs before any *get_buffer calls so
> > this check here is what is neccessary and sufficient for this specific
> > bug
> 
> If the allocation you're talking about is
> https://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavcodec/apedec.c;h=490b11b94e0b1666f18248b2b247c874fed6e0bc;hb=HEAD#l1500
> then you could just move it (and the five lines that follow it) right
> below the ff_get_buffer() call.

ill apply a patch which does the check in ff_get_buffer() at the same
point where its done for max_pixels

thx

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

The greatest way to live with honor in this world is to be what we pretend
to be. -- Socrates
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20190925/9e29f025/attachment.sig>