[FFmpeg-cvslog] avcodec/wmadec: Require previous exponents for reuse

[Michael Niedermayer]

ffmpeg | branch: release/3.4 | Michael Niedermayer <michael at niedermayer.cc> | Thu Oct 31 14:38:16 2019 +0100| [b385b34761415735c464b9560b1f64f8babc9ee6] | committer: Michael Niedermayer

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 at niedermayer.cc>
(cherry picked from commit c54b9fc42fee613e2c4c0dae2052ff94cd15e254)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b385b34761415735c464b9560b1f64f8babc9ee6
---

 libavcodec/wma.h    | 1 +
 libavcodec/wmadec.c | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/libavcodec/wma.h b/libavcodec/wma.h
index 325f03c44b..8344cb5b93 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 78b51e5871..bb9bc8d236 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 */