avformat/mov: check offset for overflow in mov_probe()

Fixes: Invalid read of size 4
Fixes: ASAN_Deadlysignal.zip

Found-by: Hardik Shah <hardik05@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mov.c

@@ -7114,7 +7114,7 @@ static int mov_probe(const AVProbeData *p)
         int64_t size;
         int minsize = 8;
         /* ignore invalid offset */
-        if ((offset + 8) > (unsigned int)p->buf_size)
+        if ((offset + 8ULL) > (unsigned int)p->buf_size)
             break;
         size = AV_RB32(p->buf + offset);
         if (size == 1 && offset + 16 <= (unsigned int)p->buf_size) {
@@ -7161,6 +7161,8 @@ static int mov_probe(const AVProbeData *p)
             score  = FFMAX(score, AVPROBE_SCORE_EXTENSION);
             break;
         }
+        if (size > INT64_MAX - offset)
+            break;
         offset += size;
     }
     if (score > AVPROBE_SCORE_MAX - 50 && moov_offset != -1) {