From: Michael Niedermayer <michael@niedermayer.cc>
Date: Thu, 31 Oct 2019 13:38:16 +0000 (+0100)
Subject: avcodec/wmadec: Require previous exponents for reuse
X-Git-Url: https://git.sesse.net/?a=commitdiff_plain;h=c54b9fc42fee613e2c4c0dae2052ff94cd15e254;p=ffmpeg

avcodec/wmadec: Require previous exponents for reuse

Fixes: division by zero
Fixes: 18474/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMAV2_fuzzer-5764986962182144

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---

diff --git a/libavcodec/wma.h b/libavcodec/wma.h
index 325f03c44b7..8344cb5b937 100644
--- a/libavcodec/wma.h
+++ b/libavcodec/wma.h
@@ -123,6 +123,7 @@ typedef struct WMACodecContext {
     uint8_t last_superframe[MAX_CODED_SUPERFRAME_SIZE + AV_INPUT_BUFFER_PADDING_SIZE]; /* padding added */
     int last_bitoffset;
     int last_superframe_len;
+    int exponents_initialized;
     float noise_table[NOISE_TAB_SIZE];
     int noise_index;
     float noise_mult; /* XXX: suppress that and integrate it in the noise array */
diff --git a/libavcodec/wmadec.c b/libavcodec/wmadec.c
index 78b51e5871b..bb9bc8d2367 100644
--- a/libavcodec/wmadec.c
+++ b/libavcodec/wmadec.c
@@ -587,6 +587,9 @@ static int wma_decode_block(WMACodecContext *s)
                 s->exponents_bsize[ch] = bsize;
             }
         }
+        s->exponents_initialized = 1;
+    }else if (!s->exponents_initialized) {
+        return AVERROR_INVALIDDATA;
     }
 
     /* parse spectral coefficients : just RLE encoding */