[FFmpeg-cvslog] avcodec/adpcm: Clip step index for ADPCM_IMA_APM

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sun Mar  1 22:30:00 2020 +0100| [ac73879f1bb27aa979a69bda24d1ca790e69f341] | committer: Michael Niedermayer

avcodec/adpcm: Clip step index for ADPCM_IMA_APM

Fixes: out of array access
Fixes: 20828/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ADPCM_IMA_APM_fuzzer-5712770106654720

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Paul B Mahol <onemda at gmail.com>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=ac73879f1bb27aa979a69bda24d1ca790e69f341
---

 libavcodec/adpcm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/adpcm.c b/libavcodec/adpcm.c
index b987e93c5f..5f152ee6ef 100644
--- a/libavcodec/adpcm.c
+++ b/libavcodec/adpcm.c
@@ -154,9 +154,9 @@ static av_cold int adpcm_decode_init(AVCodecContext * avctx)
     case AV_CODEC_ID_ADPCM_IMA_APM:
         if (avctx->extradata && avctx->extradata_size >= 16) {
             c->status[0].predictor  = AV_RL32(avctx->extradata +  0);
-            c->status[0].step_index = AV_RL32(avctx->extradata +  4);
+            c->status[0].step_index = av_clip(AV_RL32(avctx->extradata +  4), 0, 88);
             c->status[1].predictor  = AV_RL32(avctx->extradata +  8);
-            c->status[1].step_index = AV_RL32(avctx->extradata + 12);
+            c->status[1].step_index = av_clip(AV_RL32(avctx->extradata + 12), 0, 88);
         }
         break;
     case AV_CODEC_ID_ADPCM_IMA_WS: