Re: [FFmpeg-devel] [PATCH 3/3] avcodec/hevc_ps: Avoid signed overflow before check on QP

From: Michael Niedermayer <michael@niedermayer.cc>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH 3/3] avcodec/hevc_ps: Avoid signed overflow before check on QP
Date: Sun, 30 Apr 2023 21:58:36 +0200
Message-ID: <20230430195836.GL275832@pb2> (raw)
In-Reply-To: <e6c59e3c-7f56-8ed7-c8c1-7b015ec9dd84@gmail.com>

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On Thu, Apr 27, 2023 at 03:49:54PM -0300, James Almer wrote:
> On 4/27/2023 3:38 PM, Michael Niedermayer wrote:
> > Fixes: signed integer overflow: -2147483648 - 5 cannot be represented in type 'int'
> > Fixes: 58066/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HEVC_fuzzer-5312995835379712
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >   libavcodec/hevc_ps.c | 6 +++---
> >   1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/libavcodec/hevc_ps.c b/libavcodec/hevc_ps.c
> > index 1533e2a817..6b8f432609 100644
> > --- a/libavcodec/hevc_ps.c
> > +++ b/libavcodec/hevc_ps.c
> > @@ -1522,9 +1522,9 @@ static int pps_scc_extension(GetBitContext *gb, AVCodecContext *avctx,
> >       pps->pps_curr_pic_ref_enabled_flag = get_bits1(gb);
> >       if (pps->residual_adaptive_colour_transform_enabled_flag = get_bits1(gb)) {
> >           pps->pps_slice_act_qp_offsets_present_flag = get_bits1(gb);
> > -        pps->pps_act_y_qp_offset  = get_se_golomb_long(gb) - 5;
> > -        pps->pps_act_cb_qp_offset = get_se_golomb_long(gb) - 5;
> > -        pps->pps_act_cr_qp_offset = get_se_golomb_long(gb) - 3;
> > +        pps->pps_act_y_qp_offset  = get_se_golomb_long(gb) - 5U;
> > +        pps->pps_act_cb_qp_offset = get_se_golomb_long(gb) - 5U;
> > +        pps->pps_act_cr_qp_offset = get_se_golomb_long(gb) - 3U;
> 
> Spec compliant values for all of these are in the -7..17 and -9..15 range,
> so just use get_se_golomb() instead, which i assume is for small values,
> much like get_ue_golomb().

will apply with that change

thx

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Its not that you shouldnt use gotos but rather that you should write
readable code and code with gotos often but not always is less readable

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