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[FFmpeg-devel,2/2] avcodec/cbs_h2645: Avoid more cases of 0 size slices

Message ID 20200307224043.12676-2-michael@niedermayer.cc
State New
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Series [FFmpeg-devel,1/2] avcodec/cbs_jpeg: Check length for SOS
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Commit Message

Michael Niedermayer March 7, 2020, 10:40 p.m. UTC
Fixes: Assertion failure
Fixes: 19629/clusterfuzz-testcase-minimized-ffmpeg_BSF_H264_METADATA_fuzzer-5676822528524288

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/cbs_h2645.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Comments

Andreas Rheinhardt March 9, 2020, 4:57 a.m. UTC | #1
Michael Niedermayer:
> Fixes: Assertion failure
> Fixes: 19629/clusterfuzz-testcase-minimized-ffmpeg_BSF_H264_METADATA_fuzzer-5676822528524288
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/cbs_h2645.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c
> index c8347ba5fa..7427eefa30 100644
> --- a/libavcodec/cbs_h2645.c
> +++ b/libavcodec/cbs_h2645.c
> @@ -870,7 +870,8 @@ static int cbs_h264_read_nal_unit(CodedBitstreamContext *ctx,
>                         "from slice data.\n", z);
>                  len -= z;
>              }
> -
> +            if (len <= pos / 8)
> +                return AVERROR_INVALIDDATA;
>              slice->data_size = len - pos / 8;
>              slice->data_ref  = av_buffer_ref(unit->data_ref);
>              if (!slice->data_ref)
> @@ -1052,7 +1053,8 @@ static int cbs_h265_read_nal_unit(CodedBitstreamContext *ctx,
>                         "from slice data.\n", z);
>                  len -= z;
>              }
> -
> +            if (len <= pos / 8)
> +                return AVERROR_INVALIDDATA;
>              slice->data_size = len - pos / 8;
>              slice->data_ref  = av_buffer_ref(unit->data_ref);
>              if (!slice->data_ref)
> 

Imagine you have CAVLC encoded H.264 where there is nothing after the
header except zero bits and where the slice header is not
byte-aligned. Then av_assert0(temp) in cbs_h2645_write_slice_data()
will be triggered both now as well as with your patch, because your
check is too crude.

I have already sent a patch [2] for this. It presupposes [1].

- Andreas

[1]:
https://patchwork.ffmpeg.org/project/ffmpeg/patch/20191209222604.28920-5-andreas.rheinhardt@gmail.com/
[2]:
https://patchwork.ffmpeg.org/project/ffmpeg/patch/20191209222604.28920-6-andreas.rheinhardt@gmail.com/
Michael Niedermayer March 9, 2020, 9:52 p.m. UTC | #2
On Mon, Mar 09, 2020 at 05:57:50AM +0100, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: Assertion failure
> > Fixes: 19629/clusterfuzz-testcase-minimized-ffmpeg_BSF_H264_METADATA_fuzzer-5676822528524288
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >  libavcodec/cbs_h2645.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c
> > index c8347ba5fa..7427eefa30 100644
> > --- a/libavcodec/cbs_h2645.c
> > +++ b/libavcodec/cbs_h2645.c
> > @@ -870,7 +870,8 @@ static int cbs_h264_read_nal_unit(CodedBitstreamContext *ctx,
> >                         "from slice data.\n", z);
> >                  len -= z;
> >              }
> > -
> > +            if (len <= pos / 8)
> > +                return AVERROR_INVALIDDATA;
> >              slice->data_size = len - pos / 8;
> >              slice->data_ref  = av_buffer_ref(unit->data_ref);
> >              if (!slice->data_ref)
> > @@ -1052,7 +1053,8 @@ static int cbs_h265_read_nal_unit(CodedBitstreamContext *ctx,
> >                         "from slice data.\n", z);
> >                  len -= z;
> >              }
> > -
> > +            if (len <= pos / 8)
> > +                return AVERROR_INVALIDDATA;
> >              slice->data_size = len - pos / 8;
> >              slice->data_ref  = av_buffer_ref(unit->data_ref);
> >              if (!slice->data_ref)
> > 
> 
> Imagine you have CAVLC encoded H.264 where there is nothing after the
> header except zero bits and where the slice header is not
> byte-aligned. Then av_assert0(temp) in cbs_h2645_write_slice_data()
> will be triggered both now as well as with your patch, because your
> check is too crude.
> 
> I have already sent a patch [2] for this. It presupposes [1].

the assert you speak about wasnt the one failing for this.
but your patches are a nicer solution so ill apply them

Thanks


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diff mbox series

Patch

diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c
index c8347ba5fa..7427eefa30 100644
--- a/libavcodec/cbs_h2645.c
+++ b/libavcodec/cbs_h2645.c
@@ -870,7 +870,8 @@  static int cbs_h264_read_nal_unit(CodedBitstreamContext *ctx,
                        "from slice data.\n", z);
                 len -= z;
             }
-
+            if (len <= pos / 8)
+                return AVERROR_INVALIDDATA;
             slice->data_size = len - pos / 8;
             slice->data_ref  = av_buffer_ref(unit->data_ref);
             if (!slice->data_ref)
@@ -1052,7 +1053,8 @@  static int cbs_h265_read_nal_unit(CodedBitstreamContext *ctx,
                        "from slice data.\n", z);
                 len -= z;
             }
-
+            if (len <= pos / 8)
+                return AVERROR_INVALIDDATA;
             slice->data_size = len - pos / 8;
             slice->data_ref  = av_buffer_ref(unit->data_ref);
             if (!slice->data_ref)