MPEG4Extractor: ensure buffer size is not less than 8 for LastCommentData.

Bug: 24346430
Change-Id: I897a724e968841d9160f819d06c0ce22f6d743c4
(cherry picked from commit 5cae16b)
(cherry picked from commit e6d904f)

Author: Wei Jia

media/libstagefright/MPEG4Extractor.cpp

@@ -2153,6 +2153,12 @@ status_t MPEG4Extractor::parseMetaData(off64_t offset, size_t size) {
                     mLastCommentName.setTo((const char *)buffer + 4);
                     break;
                 case FOURCC('d', 'a', 't', 'a'):
+                    if (size < 8) {
+                        delete[] buffer;
+                        buffer = NULL;
+                        ALOGE("b/24346430");
+                        return ERROR_MALFORMED;
+                    }
                     mLastCommentData.setTo((const char *)buffer + 8);
                     break;
             }