[FFmpeg-devel] [PATCH] avcodec/msp2dec: Check available space in RLE decoder

[Andreas Rheinhardt]

Michael Niedermayer:
> Fixes: out of array read
> Fixes: 32968/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MSP2_fuzzer-5315296027082752
> 
> 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/msp2dec.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/msp2dec.c b/libavcodec/msp2dec.c
> index cc548d218a..87057fb5e2 100644
> --- a/libavcodec/msp2dec.c
> +++ b/libavcodec/msp2dec.c
> @@ -68,9 +68,10 @@ static int msp2_decode_frame(AVCodecContext *avctx,
>  
>          bytestream2_init(&gb, buf, pkt_size);
>          x = 0;
> -        while (bytestream2_get_bytes_left(&gb) && x < width) {
> +        while (bytestream2_get_bytes_left(&gb) > 0 && x < width) {

This decoder uses the checked bytestream2 API, so != 0 and > 0 should be
equivalent for bytestream2_get_bytes_left(&gb).

>              int size = bytestream2_get_byte(&gb);
>              if (size) {
> +                size = FFMIN(size, bytestream2_get_bytes_left(&gb));
>                  memcpy(p->data[0] + y * p->linesize[0] + x, gb.buffer, FFMIN(size, width - x));

width can include seven bytes of the packet's padding, but it stays
within the padding, so I wonder where the out of array read comes from.
The only fishy thing in this decoder I see is that 2 * avctx->height
might overflow.

>                  bytestream2_skip(&gb, size);
>              } else {
>