[FFmpeg-devel] [PATCH] Support limiting the number of pixels per image

[wm4]

On Thu,  8 Dec 2016 19:30:25 +0100
Michael Niedermayer <michael at niedermayer.cc> wrote:

> TODO: split into 2 patches (one per lib), docs & bump
> 
> This allows preventing some OOM and "slow decoding" cases by limiting the maximum resolution
> this may be useful to avoid fuzzers getting stuck in boring cases
> 
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavcodec/avcodec.h                 |  8 ++++++++
>  libavcodec/options_table.h           |  1 +
>  libavutil/imgutils.c                 | 22 ++++++++++++++++++----
>  tests/ref/fate/api-mjpeg-codec-param |  2 ++
>  tests/ref/fate/api-png-codec-param   |  2 ++
>  5 files changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> index 7ac2adaf66..81052b10ef 100644
> --- a/libavcodec/avcodec.h
> +++ b/libavcodec/avcodec.h
> @@ -3570,6 +3570,14 @@ typedef struct AVCodecContext {
>       */
>      int trailing_padding;
>  
> +    /**
> +     * The number of pixels per image to maximally accept.
> +     *
> +     * - decoding: set by user
> +     * - encoding: unused
> +     */
> +    int max_pixels;
> +
>  } AVCodecContext;
>  
>  AVRational av_codec_get_pkt_timebase         (const AVCodecContext *avctx);
> diff --git a/libavcodec/options_table.h b/libavcodec/options_table.h
> index ee79859953..2f5eb252fe 100644
> --- a/libavcodec/options_table.h
> +++ b/libavcodec/options_table.h
> @@ -570,6 +570,7 @@ static const AVOption avcodec_options[] = {
>  {"codec_whitelist", "List of decoders that are allowed to be used", OFFSET(codec_whitelist), AV_OPT_TYPE_STRING, { .str = NULL },  CHAR_MIN, CHAR_MAX, A|V|S|D },
>  {"pixel_format", "set pixel format", OFFSET(pix_fmt), AV_OPT_TYPE_PIXEL_FMT, {.i64=AV_PIX_FMT_NONE}, -1, INT_MAX, 0 },
>  {"video_size", "set video size", OFFSET(width), AV_OPT_TYPE_IMAGE_SIZE, {.str=NULL}, 0, INT_MAX, 0 },
> +{"max_pixels", "Maximum number of pixels", OFFSET(max_pixels), AV_OPT_TYPE_INT, {.i64 = INT_MAX }, 0, INT_MAX, A|V|S|D },
>  {NULL},
>  };
>  
> diff --git a/libavutil/imgutils.c b/libavutil/imgutils.c
> index 37808e53d0..7c42ec7e17 100644
> --- a/libavutil/imgutils.c
> +++ b/libavutil/imgutils.c
> @@ -30,6 +30,7 @@
>  #include "mathematics.h"
>  #include "pixdesc.h"
>  #include "rational.h"
> +#include "opt.h"
>  
>  void av_image_fill_max_pixsteps(int max_pixsteps[4], int max_pixstep_comps[4],
>                                  const AVPixFmtDescriptor *pixdesc)
> @@ -256,11 +257,24 @@ int av_image_check_size(unsigned int w, unsigned int h, int log_offset, void *lo
>          .log_ctx    = log_ctx,
>      };
>  
> -    if ((int)w>0 && (int)h>0 && (w+128)*(uint64_t)(h+128) < INT_MAX/8)
> -        return 0;
> +    if ((int)w<=0 || (int)h<=0 || (w+128)*(uint64_t)(h+128) >= INT_MAX/8) {
> +        av_log(&imgutils, AV_LOG_ERROR, "Picture size %ux%u is invalid\n", w, h);
> +        return AVERROR(EINVAL);
> +    }
>  
> -    av_log(&imgutils, AV_LOG_ERROR, "Picture size %ux%u is invalid\n", w, h);
> -    return AVERROR(EINVAL);
> +    if (log_ctx) {
> +        int64_t max = INT_MAX;
> +        if (av_opt_get_int(log_ctx, "max_pixels",  AV_OPT_SEARCH_CHILDREN, &max) >= 0) {

IMHO terrible implementation. Just add a new function that takes an
honest argument?

> +            if (w*h > max) {
> +                av_log(&imgutils, AV_LOG_ERROR,
> +                       "Picture size %ux%u exceeds specified max pixel count %"PRId64"\n",
> +                       w, h, max);
> +                return AVERROR(EINVAL);
> +            }
> +        }
> +    }
> +
> +    return 0;
>  }
>  
>  int av_image_check_sar(unsigned int w, unsigned int h, AVRational sar)
> diff --git a/tests/ref/fate/api-mjpeg-codec-param b/tests/ref/fate/api-mjpeg-codec-param
> index c67d1b1ab0..08313adab3 100644
> --- a/tests/ref/fate/api-mjpeg-codec-param
> +++ b/tests/ref/fate/api-mjpeg-codec-param
> @@ -155,6 +155,7 @@ stream=0, decode=0
>      codec_whitelist=
>      pixel_format=yuvj422p
>      video_size=400x225
> +    max_pixels=2147483647
>  stream=0, decode=1
>      b=0
>      ab=0
> @@ -312,3 +313,4 @@ stream=0, decode=1
>      codec_whitelist=
>      pixel_format=yuvj422p
>      video_size=400x225
> +    max_pixels=2147483647
> diff --git a/tests/ref/fate/api-png-codec-param b/tests/ref/fate/api-png-codec-param
> index bd53441894..7a9a921461 100644
> --- a/tests/ref/fate/api-png-codec-param
> +++ b/tests/ref/fate/api-png-codec-param
> @@ -155,6 +155,7 @@ stream=0, decode=0
>      codec_whitelist=
>      pixel_format=rgba
>      video_size=128x128
> +    max_pixels=2147483647
>  stream=0, decode=1
>      b=0
>      ab=0
> @@ -312,3 +313,4 @@ stream=0, decode=1
>      codec_whitelist=
>      pixel_format=rgba
>      video_size=128x128
> +    max_pixels=2147483647

In general I'd rather have the current pixel limit _removed_. It causes
problems with processing high-res images.