[FFmpeg-devel] [PATCH] avcodec/faxcompr: Check for end of bitstream in decode_group3_1d_line() and decode_group3_2d_line()

[Andreas Rheinhardt]

Michael Niedermayer:
> Fixes: infinite loop
> Fixes: 33674/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TIFF_fuzzer-4816457818046464
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavcodec/faxcompr.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/libavcodec/faxcompr.c b/libavcodec/faxcompr.c
> index 7bf11d80ca..1fc4aca0b3 100644
> --- a/libavcodec/faxcompr.c
> +++ b/libavcodec/faxcompr.c
> @@ -209,6 +209,8 @@ static int decode_group3_1d_line(AVCodecContext *avctx, GetBitContext *gb,
>      unsigned int run = 0;
>      unsigned int t;
>      for (;;) {
> +        if (get_bits_left(gb) <= 0)
> +            return AVERROR_INVALIDDATA;
>          t    = get_vlc2(gb, ccitt_vlc[mode].table, 9, 2);
>          run += t;
>          if (t < 64) {
> @@ -254,6 +256,8 @@ static int decode_group3_2d_line(AVCodecContext *avctx, GetBitContext *gb,
>      unsigned int offs = 0, run = 0;
>  
>      while (offs < width) {
> +        if (get_bits_left(gb) <= 0)
> +            return AVERROR_INVALIDDATA;

This will give the typical statement-before-declaration warning.

>          int cmode = get_vlc2(gb, ccitt_group3_2d_vlc.table, 9, 1);
>          if (cmode == -1) {
>              av_log(avctx, AV_LOG_ERROR, "Incorrect mode VLC\n");
>