[FFmpeg-devel] Re: [PATCH] avcodec/rv60dec: add upper bound check for qp

[Reaxx via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

Thanks for reviewing and applying the patch. Apologies for the incorrect
commit message , I appreciate you correcting it. Thanks again

On Fri, 7 Nov 2025 at 22:14, Michael Niedermayer via ffmpeg-devel <
ffmpeg-devel@ffmpeg.org> wrote:

> Hi Reaxx
>
> On Fri, Nov 07, 2025 at 06:20:38PM +0100, Reaxx via ffmpeg-devel wrote:
> > This patch fixes an out-of-bounds read in the RV60 decoder where qp can
> > reach 65, exceeding the rv60_qp_to_idx[64] array bounds. The previous fix
> > (61cbcaf93f) only covered intra frames. This adds validation at the
> source
> > for all frame types.
>
> >  rv60dec.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 57b6f4d726a8d8959a14807b0fa1fb162ce7bd74
> /var0001-avcodec-rv60dec-add-upper-bound-check-for-qp.patch
> > From c7a4ef1c2d235e73be849028c145949eac6ae9ef Mon Sep 17 00:00:00 2001
> > From: oblivionsage <cookieandcream560@gmail.com>
> > Date: Fri, 7 Nov 2025 18:08:14 +0100
> > Subject: [PATCH] avcodec/rv60dec: add upper bound check for qp
> >
> > The quantization parameter (qp) can exceed 63 when the base value
> > from frame header (0-63) is combined with the offset from slice data
> > (up to +2), resulting in qp=65. This causes out-of-bounds access to
> > the rv60_qp_to_idx[64] array in decode_cbp8(), decode_cbp16(), and
> > get_c4x4_set().
> >
>
> > Previous fix in commit 61cbcaf93f3b2e10124f4c63ce7cd8dad6505fb2 added
> validation only for intra
> > frames at a later stage. This patch adds validation at the source
> > in decode_slice() to prevent invalid qp values for all frame types.
>
> This is not correct, the current code is not just checking qp in the
> intra case
>
>
> >
> > Fixes: Out-of-bounds read reported by OSS-Fuzz
> (clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_RV60_fuzzer-5160167345291264)
>
> This is incorrect, this testcase does not trigger the issue fixed in this
> patch
>
> There is in fact no testcase for the issue this fixes to the best of
> my knowledge.
>
> i will apply this with a corrected commit message
>
> thx
>
>
> [...]
>
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> I have often repented speaking, but never of holding my tongue.
> -- Xenocrates
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