[FFmpeg-cvslog] avcodec/diracdec: Fix off by 1 error in quant check

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Thu May 25 16:35:40 2017 +0200| [b946bd8ef2c7aeee09469a4901182a44f9b67189] | committer: Michael Niedermayer

avcodec/diracdec: Fix off by 1 error in quant check

Fixes: out of array read
Fixes: 1781/clusterfuzz-testcase-minimized-4617176877105152

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b946bd8ef2c7aeee09469a4901182a44f9b67189
---

 libavcodec/diracdec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/diracdec.c b/libavcodec/diracdec.c
index 601d701bc8..c031b40b5e 100644
--- a/libavcodec/diracdec.c
+++ b/libavcodec/diracdec.c
@@ -823,7 +823,7 @@ static int decode_hq_slice(DiracContext *s, DiracSlice *slice, uint8_t *tmp_buf)
     skip_bits_long(gb, 8*s->highquality.prefix_bytes);
     quant_idx = get_bits(gb, 8);
 
-    if (quant_idx > DIRAC_MAX_QUANT_INDEX) {
+    if (quant_idx > DIRAC_MAX_QUANT_INDEX - 1) {
         av_log(s->avctx, AV_LOG_ERROR, "Invalid quantization index - %i\n", quant_idx);
         return AVERROR_INVALIDDATA;
     }