Re: [FFmpeg-devel] [PATCH 2/4] avformat/jpegxl_anim_dec: initialize bit buffer

From: Kacper Michajlow <kasper93@gmail.com>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH 2/4] avformat/jpegxl_anim_dec: initialize bit buffer
Date: Mon, 5 Aug 2024 02:08:06 +0200
Message-ID: <CABPLASTDQMahRcoNpXHUGQD_DNv2AL2vMi9hW2SmqsJxv+b0LA@mail.gmail.com> (raw)
In-Reply-To: <20240804142315.1430389-2-michael@niedermayer.cc>

On Sun, 4 Aug 2024 at 16:23, Michael Niedermayer <michael@niedermayer.cc> wrote:
>
> Fixes: use-of-uninitialized-value
> Fixes: 70837/clusterfuzz-testcase-minimized-ffmpeg_dem_JPEGXL_ANIM_fuzzer-5089407768526848
>
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavformat/jpegxl_anim_dec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavformat/jpegxl_anim_dec.c b/libavformat/jpegxl_anim_dec.c
> index ac95d3b9617..3045167e1f9 100644
> --- a/libavformat/jpegxl_anim_dec.c
> +++ b/libavformat/jpegxl_anim_dec.c
> @@ -77,7 +77,7 @@ static int jpegxl_anim_read_header(AVFormatContext *s)
>      JXLAnimDemuxContext *ctx = s->priv_data;
>      AVIOContext *pb = s->pb;
>      AVStream *st;
> -    uint8_t head[256 + AV_INPUT_BUFFER_PADDING_SIZE];
> +    uint8_t head[256 + AV_INPUT_BUFFER_PADDING_SIZE] = {0};
>      const int sizeofhead = sizeof(head) - AV_INPUT_BUFFER_PADDING_SIZE;
>      int headsize = 0, ret;
>      FFJXLMetadata meta = { 0 };
> --
> 2.45.2

Not sure it is required to zero the whole buffer. I sent an
alternative patch some time ago, which clears only the relevant area.
https://patchwork.ffmpeg.org/project/ffmpeg/patch/20240627004037.1336-4-kasper93@gmail.com/

- Kacper
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