[FFmpeg-cvslog] avcodec/vp3: Check remaining bits in unpack_dct_coeffs()

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Mon May  1 18:46:27 2017 +0200| [2f00300b779e7b247c85db0d7daef448225105ff] | committer: Michael Niedermayer

avcodec/vp3: Check remaining bits in unpack_dct_coeffs()

Decreases the time spend decoding junk.

May fix: 1283/clusterfuzz-testcase-minimized-6221126759874560

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=2f00300b779e7b247c85db0d7daef448225105ff
---

 libavcodec/vp3.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/libavcodec/vp3.c b/libavcodec/vp3.c
index 86e5852e32..b10cb39f8a 100644
--- a/libavcodec/vp3.c
+++ b/libavcodec/vp3.c
@@ -1071,6 +1071,9 @@ static int unpack_dct_coeffs(Vp3DecodeContext *s, GetBitContext *gb)
 
     s->dct_tokens[0][0] = s->dct_tokens_base;
 
+    if (get_bits_left(gb) < 16)
+        return AVERROR_INVALIDDATA;
+
     /* fetch the DC table indexes */
     dc_y_table = get_bits(gb, 4);
     dc_c_table = get_bits(gb, 4);
@@ -1080,6 +1083,8 @@ static int unpack_dct_coeffs(Vp3DecodeContext *s, GetBitContext *gb)
                                    0, residual_eob_run);
     if (residual_eob_run < 0)
         return residual_eob_run;
+    if (get_bits_left(gb) < 8)
+        return AVERROR_INVALIDDATA;
 
     /* reverse prediction of the Y-plane DC coefficients */
     reverse_dc_prediction(s, 0, s->fragment_width[0], s->fragment_height[0]);
@@ -1102,6 +1107,8 @@ static int unpack_dct_coeffs(Vp3DecodeContext *s, GetBitContext *gb)
                               s->fragment_width[1], s->fragment_height[1]);
     }
 
+    if (get_bits_left(gb) < 8)
+        return AVERROR_INVALIDDATA;
     /* fetch the AC table indexes */
     ac_y_table = get_bits(gb, 4);
     ac_c_table = get_bits(gb, 4);