[FFmpeg-devel] [PATCH] avcodec/msp2dec: Check available space in RLE decoder
Andreas Rheinhardt
andreas.rheinhardt at outlook.com
Wed Apr 7 01:42:50 EEST 2021
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 {
>
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