matroskadec: Check EBML lace sizes.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/matroskadec.c

@@ -2027,10 +2027,10 @@ static int matroska_parse_laces(MatroskaDemuxContext *matroska, uint8_t **buf,
         uint64_t num;
         uint64_t total;
         n = matroska_ebmlnum_uint(matroska, data, size, &num);
-        if (n < 0) {
+        if (n < 0 || num > INT_MAX) {
             av_log(matroska->ctx, AV_LOG_INFO,
                    "EBML block data error\n");
-            res = n;
+            res = n<0 ? n : AVERROR_INVALIDDATA;
             break;
         }
         data += n;
@@ -2040,10 +2040,10 @@ static int matroska_parse_laces(MatroskaDemuxContext *matroska, uint8_t **buf,
             int64_t snum;
             int r;
             r = matroska_ebmlnum_sint(matroska, data, size, &snum);
-            if (r < 0) {
+            if (r < 0 || lace_size[n - 1] + snum > (uint64_t)INT_MAX) {
                 av_log(matroska->ctx, AV_LOG_INFO,
                        "EBML block data error\n");
-                res = r;
+                res = r<0 ? r : AVERROR_INVALIDDATA;
                 break;
             }
             data += r;