Fixes issue 890: OOM with zmbv file

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

libavformat/avidec.c

@@ -544,6 +544,10 @@ static int avi_read_header(AVFormatContext *s, AVFormatParameters *ap)
             st->start_time = 0;
             avio_rl32(pb); /* buffer size */
             avio_rl32(pb); /* quality */
+            if (ast->cum_len*ast->scale/ast->rate > 3600) {
+                av_log(s, AV_LOG_ERROR, "crazy start time, iam scared, giving up\n");
+                return AVERROR_INVALIDDATA;
+            }
             ast->sample_size = avio_rl32(pb); /* sample ssize */
             ast->cum_len *= FFMAX(1, ast->sample_size);
 //            av_log(s, AV_LOG_DEBUG, "%d %d %d %d\n", ast->rate, ast->scale, ast->start, ast->sample_size);