lavf/mov.c: Avoid heap allocation wraps in mov_read_{senc,saiz}()

Core of patch is from paul@paulmehta.com
Reference https://crbug.com/643952 (senc,saiz portions)

Signed-off-by: Matt Wolenetz <wolenetz@chromium.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mov.c

@@ -4968,8 +4968,8 @@ static int mov_read_senc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
     avio_rb32(pb);        /* entries */
 
-    if (atom.size < 8) {
-        av_log(c->fc, AV_LOG_ERROR, "senc atom size %"PRId64" too small\n", atom.size);
+    if (atom.size < 8 || atom.size > FFMIN(INT_MAX, SIZE_MAX)) {
+        av_log(c->fc, AV_LOG_ERROR, "senc atom size %"PRId64" invalid\n", atom.size);
         return AVERROR_INVALIDDATA;
     }
 
@@ -5037,6 +5037,11 @@ static int mov_read_saiz(MOVContext *c, AVIOContext *pb, MOVAtom atom)
         return 0;
     }
 
+    if (atom.size > FFMIN(INT_MAX, SIZE_MAX)) {
+        av_log(c->fc, AV_LOG_ERROR, "saiz atom auxiliary_info_sizes size %"PRId64" invalid\n", atom.size);
+        return AVERROR_INVALIDDATA;
+    }
+
     /* save the auxiliary info sizes as is */
     data_size = atom.size - atom_header_size;