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

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

Hi Michael,

Yes, the commit message LGTM , Thank you for the detailed explanation and
for taking the time to review this thoroughly. I appreciate your patience.

On Fri, 7 Nov 2025 at 22:39, Michael Niedermayer via ffmpeg-devel <
ffmpeg-devel@ffmpeg.org> wrote:

> Hi
>
> On Fri, Nov 07, 2025 at 10:19:27PM +0100, Reaxx via ffmpeg-devel wrote:
> > Thanks for reviewing and applying the patch. Apologies for the incorrect
> > commit message , I appreciate you correcting it. Thanks again
>
> actually, can you check if my commit message is correct before i apply it ?
>
> commit 3adc44bce403bf0841d7c1a933f2635037a762f8 (HEAD -> master)
> Author: oblivionsage <cookieandcream560@gmail.com>
> Date:   Fri Nov 7 18:08:14 2025 +0100
>
>     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().
>
>     Fixes: Out-of-bounds read
>     Signed-off-by: oblivionsage <cookieandcream560@gmail.com>
>
>     No testsample is available
>
>     This is related to 61cbcaf93f3b2e10124f4c63ce7cd8dad6505fb2 and
> clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_RV60_fuzzer-5160167345291264
>     which fixed rv60_qp_to_idx[qp + 32] out of array access
>     These 2 checks are not redundant and neither covers the cases of the
> other
>
>     Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
>
> diff --git a/libavcodec/rv60dec.c b/libavcodec/rv60dec.c
> index 33728e33a06..b7b4f46512e 100644
> --- a/libavcodec/rv60dec.c
> +++ b/libavcodec/rv60dec.c
> @@ -2265,7 +2265,7 @@ static int decode_slice(AVCodecContext *avctx, void
> *tdata, int cu_y, int thread
>              ff_thread_progress_await(&s->progress[cu_y - 1], cu_x + 2);
>
>          qp = s->qp + read_qp_offset(&gb, s->qp_off_type);
> -        if (qp < 0) {
> +        if (qp < 0 || qp >= 64) {
>              ret = AVERROR_INVALIDDATA;
>              break;
>
>
> [...]
>
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> Complexity theory is the science of finding the exact solution to an
> approximation. Benchmarking OTOH is finding an approximation of the exact
> _______________________________________________
> ffmpeg-devel mailing list -- ffmpeg-devel@ffmpeg.org
> To unsubscribe send an email to ffmpeg-devel-leave@ffmpeg.org
>
_______________________________________________
ffmpeg-devel mailing list -- ffmpeg-devel@ffmpeg.org
To unsubscribe send an email to ffmpeg-devel-leave@ffmpeg.org