[FFmpeg-cvslog] avcodec/wmadec: Keep track of exponent initialization per channel

[Michael Niedermayer]

ffmpeg | branch: release/2.8 | Michael Niedermayer <michael at niedermayer.cc> | Sat Nov 30 16:46:46 2019 +0100| [a35b01b84ae32d401bd6ec81a7cff5d369a8394a] | committer: Michael Niedermayer

avcodec/wmadec: Keep track of exponent initialization per channel

Fixes: division by 0
Fixes: 19123/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMAV2_fuzzer-5655493121146880

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 bf5c850b795126d4f60dd9498c06f0492f5726a7)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=a35b01b84ae32d401bd6ec81a7cff5d369a8394a
---

 libavcodec/wma.h    | 2 +-
 libavcodec/wmadec.c | 9 ++++++---
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/libavcodec/wma.h b/libavcodec/wma.h
index ec618d1e64..3126df7ebe 100644
--- a/libavcodec/wma.h
+++ b/libavcodec/wma.h
@@ -123,7 +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;
+    int exponents_initialized[MAX_CHANNELS];
     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 adf8e491c1..745e29b34b 100644
--- a/libavcodec/wmadec.c
+++ b/libavcodec/wmadec.c
@@ -584,11 +584,14 @@ static int wma_decode_block(WMACodecContext *s)
                     decode_exp_lsp(s, ch);
                 }
                 s->exponents_bsize[ch] = bsize;
+                s->exponents_initialized[ch] = 1;
             }
         }
-        s->exponents_initialized = 1;
-    }else if (!s->exponents_initialized) {
-        return AVERROR_INVALIDDATA;
+    }
+
+    for (ch = 0; ch < s->avctx->channels; ch++) {
+        if (s->channel_coded[ch] && !s->exponents_initialized[ch])
+            return AVERROR_INVALIDDATA;
     }
 
     /* parse spectral coefficients : just RLE encoding */