[FFmpeg-cvslog] diracdec: Check for negative quants which would cause out of array reads.

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michaelni at gmx.at> | Sun Jan 29 05:04:25 2012 +0100| [5cd8afee99c83b62e1474f122d947de7e4ad9ff5] | committer: Michael Niedermayer

diracdec: Check for negative quants which would cause out of array reads.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=5cd8afee99c83b62e1474f122d947de7e4ad9ff5
---

 libavcodec/diracdec.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/libavcodec/diracdec.c b/libavcodec/diracdec.c
index c96b37a..049f759 100644
--- a/libavcodec/diracdec.c
+++ b/libavcodec/diracdec.c
@@ -491,10 +491,16 @@ static inline void codeblock(DiracContext *s, SubBand *b,
     }
 
     if (s->codeblock_mode && !(s->old_delta_quant && blockcnt_one)) {
+        int quant = b->quant;
         if (is_arith)
-            b->quant += dirac_get_arith_int(c, CTX_DELTA_Q_F, CTX_DELTA_Q_DATA);
+            quant += dirac_get_arith_int(c, CTX_DELTA_Q_F, CTX_DELTA_Q_DATA);
         else
-            b->quant += dirac_get_se_golomb(gb);
+            quant += dirac_get_se_golomb(gb);
+        if (quant < 0) {
+            av_log(s->avctx, AV_LOG_ERROR, "Invalid quant\n");
+            return;
+        }
+        b->quant = quant;
     }
 
     b->quant = FFMIN(b->quant, MAX_QUANT);