[libav-commits] vc1: check that slices have a positive height

[Anton Khirnov]

Module: libav
Branch: master
Commit: 33f10546ec012ad4e1054b57317885cded7e953e

Author:    Anton Khirnov <an...@khirnov.net>
Committer: Anton Khirnov <an...@khirnov.net>
Date:      Sun Aug 14 10:18:39 2016 +0200

vc1: check that slices have a positive height

Fixes possible invalid reads.

CC: libav-sta...@libav.org
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind

---

 libavcodec/vc1dec.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
index 3d042d0..b26fbf2 100644
--- a/libavcodec/vc1dec.c
+++ b/libavcodec/vc1dec.c
@@ -881,6 +881,12 @@ static int vc1_decode_frame(AVCodecContext *avctx, void 
*data,
                 s->end_mb_y = (i == n_slices     ) ? mb_height : 
FFMIN(mb_height, slices[i].mby_start % mb_height);
             else
                 s->end_mb_y = (i <= n_slices1 + 1) ? mb_height : 
FFMIN(mb_height, slices[i].mby_start % mb_height);
+
+            if (s->end_mb_y <= s->start_mb_y) {
+                av_log(v->s.avctx, AV_LOG_ERROR, "Invalid slice size\n");
+                goto err;
+            }
+
             ff_vc1_decode_blocks(v);
             if (i != n_slices)
                 s->gb = slices[i].gb;

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