Re: [FFmpeg-devel] [PATCH 2/6] avformat/mov: Check that tile_item_list is initialized in read_image_iovl()

[James Almer <jamrial@gmail.com>]

On 4/1/2024 5:56 PM, Michael Niedermayer wrote:
> Fixes: null pointer dereference
> Fixes: 67494/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-6528714521247744
> 
> 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 | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 7bdeeb99f98..fa4c237c0d8 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -9364,6 +9364,10 @@ static int read_image_iovl(AVFormatContext *s, const HEIFGrid *grid,
>       }
>   
>       for (int i = 0; i < tile_grid->nb_tiles; i++) {
> +        if (!grid->tile_item_list[i]) {
> +            ret = AVERROR_INVALIDDATA;
> +            goto fail;
> +        }

This should not happen. We shouldn't get this far if the array was not 
filled.

Can you please test the following?

> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 7bdeeb99f9..fb0113b149 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -9397,8 +9397,9 @@ static int mov_parse_tiles(AVFormatContext *s)
> 
>          for (int j = 0; j < grid->nb_tiles; j++) {
>              int tile_id = grid->tile_id_list[j];
> +            int k;
> 
> -            for (int k = 0; k < mov->nb_heif_item; k++) {
> +            for (k = 0; k < mov->nb_heif_item; k++) {
>                  HEIFItem *item = &mov->heif_item[k];
>                  AVStream *st = item->st;
> 
> @@ -9424,6 +9425,13 @@ static int mov_parse_tiles(AVFormatContext *s)
>                  break;
>              }
> 
> +            if (k == grid->nb_tiles) {
> +                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);
> +                ff_remove_stream_group(s, stg);
> +                loop = 0;
> +            }
>              if (!loop)
>                  break;
>          }
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