[FFmpeg-cvslog] avcodec/ralf: Check num_blocks before use

[Michael Niedermayer]

ffmpeg | branch: release/2.8 | Michael Niedermayer <michael at niedermayer.cc> | Mon May 11 22:17:43 2020 +0200| [f8da048589640353cee66540dc3f14beaba55321] | committer: Michael Niedermayer

avcodec/ralf: Check num_blocks before use

Fixes: out of array access
Fixes: 20659/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_RALF_fuzzer-5739471895265280

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit f0c0471075fe52ed31c46e038df4280aef5b67a1)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=f8da048589640353cee66540dc3f14beaba55321
---

 libavcodec/ralf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libavcodec/ralf.c b/libavcodec/ralf.c
index ba86e7ba49..c38bdabfcd 100644
--- a/libavcodec/ralf.c
+++ b/libavcodec/ralf.c
@@ -482,6 +482,8 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame_ptr,
     init_get_bits(&gb, src + 2, table_size);
     ctx->num_blocks = 0;
     while (get_bits_left(&gb) > 0) {
+        if (ctx->num_blocks >= FF_ARRAY_ELEMS(ctx->block_size))
+            return AVERROR_INVALIDDATA;
         ctx->block_size[ctx->num_blocks] = get_bits(&gb, 15);
         if (get_bits1(&gb)) {
             ctx->block_pts[ctx->num_blocks] = get_bits(&gb, 9);