vc1: check that slices have a positive height
authorAnton Khirnov <anton@khirnov.net>
Sun, 14 Aug 2016 08:18:39 +0000 (10:18 +0200)
committerAnton Khirnov <anton@khirnov.net>
Thu, 18 Aug 2016 15:06:46 +0000 (17:06 +0200)
Fixes possible invalid reads.

CC: libav-stable@libav.org
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
libavcodec/vc1dec.c

index 3d042d0..b26fbf2 100644 (file)
@@ -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;