Re: [FFmpeg-devel] [PATCH 1/6] avformat/mov: Check tile_item_list

[James Almer <jamrial@gmail.com>]

On 4/26/2024 12:08 AM, Michael Niedermayer wrote:
> Fixes: Null pointer dereference
> Fixes: 67861/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5352628142800896
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>   libavformat/mov.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index ecd29a7d08b..97a24e6737e 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -9289,6 +9289,9 @@ static int read_image_grid(AVFormatContext *s, const HEIFGrid *grid,
>       if (tile_grid->nb_tiles != size)
>           return AVERROR_INVALIDDATA;
>   
> +    for (int i = 0; i < size; i++)
> +        if (!grid->tile_item_list[i])
> +            return AVERROR_INVALIDDATA;
>       for (int i = 0; i < tile_cols; i++)
>           tile_grid->coded_width  += grid->tile_item_list[i]->width;
>       for (int i = 0; i < size; i += tile_cols)

We shouldn't get this far if that's NULL. Does the following also work?

> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index ecd29a7d08..b21c4b6f3c 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -9440,7 +9440,7 @@ static int mov_parse_tiles(AVFormatContext *s)
>                  break;
>              }
> 
> -            if (k == grid->nb_tiles) {
> +            if (k == mov->nb_heif_item) {
>                  av_log(s, AV_LOG_WARNING, "HEIF item id %d referenced by grid id %d doesn't "
>                                            "exist\n",
>                         tile_id, grid->item->item_id);
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