diff --git a/media/libmedia/IDataSource.cpp b/media/libmedia/IDataSource.cpp
index 51c9938..5ad39fe 100644
--- a/media/libmedia/IDataSource.cpp
+++ b/media/libmedia/IDataSource.cpp
@@ -54,8 +54,16 @@
         data.writeInterfaceToken(IDataSource::getInterfaceDescriptor());
         data.writeInt64(offset);
         data.writeInt64(size);
-        remote()->transact(READ_AT, data, &reply);
-        return reply.readInt64();
+        status_t err = remote()->transact(READ_AT, data, &reply);
+        if (err != OK) {
+            return err;
+        }
+        int64_t value = 0;
+        err = reply.readInt64(&value);
+        if (err != OK) {
+            return err;
+        }
+        return (ssize_t)value;
     }
 
     virtual status_t getSize(off64_t* size) {
diff --git a/media/libstagefright/MPEG4Extractor.cpp b/media/libstagefright/MPEG4Extractor.cpp
index d014b2a..1dfa868 100644
--- a/media/libstagefright/MPEG4Extractor.cpp
+++ b/media/libstagefright/MPEG4Extractor.cpp
@@ -72,6 +72,7 @@
                 Vector<SidxEntry> &sidx,
                 const Trex *trex,
                 off64_t firstMoofOffset);
+    virtual status_t init();
 
     virtual status_t start(MetaData *params = NULL);
     virtual status_t stop();
@@ -2148,7 +2149,10 @@
             *offset += chunk_size;
 
             if (underQTMetaPath(mPath, 3)) {
-                parseQTMetaKey(data_offset, chunk_data_size);
+                status_t err = parseQTMetaKey(data_offset, chunk_data_size);
+                if (err != OK) {
+                    return err;
+                }
             }
             break;
         }
@@ -2307,7 +2311,10 @@
 
         case FOURCC('s', 'i', 'd', 'x'):
         {
-            parseSegmentIndex(data_offset, chunk_data_size);
+            status_t err = parseSegmentIndex(data_offset, chunk_data_size);
+            if (err != OK) {
+                return err;
+            }
             *offset += chunk_size;
             return UNKNOWN_ERROR; // stop parsing after sidx
         }
@@ -2349,7 +2356,10 @@
             // check if we're parsing 'ilst' for meta keys
             // if so, treat type as a number (key-id).
             if (underQTMetaPath(mPath, 3)) {
-                parseQTMetaVal(chunk_type, data_offset, chunk_data_size);
+                status_t err = parseQTMetaVal(chunk_type, data_offset, chunk_data_size);
+                if (err != OK) {
+                    return err;
+                }
             }
 
             *offset += chunk_size;
@@ -3183,9 +3193,13 @@
         }
     }
 
-    return new MPEG4Source(this,
+    sp<MPEG4Source> source =  new MPEG4Source(this,
             track->meta, mDataSource, track->timescale, track->sampleTable,
             mSidxEntries, trex, mMoofOffset);
+    if (source->init() != OK) {
+        return NULL;
+    }
+    return source;
 }
 
 // static
@@ -3582,6 +3596,7 @@
       mTrex(trex),
       mFirstMoofOffset(firstMoofOffset),
       mCurrentMoofOffset(firstMoofOffset),
+      mNextMoofOffset(-1),
       mCurrentTime(0),
       mCurrentSampleInfoAllocSize(0),
       mCurrentSampleInfoSizes(NULL),
@@ -3646,10 +3661,14 @@
 
     CHECK(format->findInt32(kKeyTrackID, &mTrackId));
 
+}
+
+status_t MPEG4Source::init() {
     if (mFirstMoofOffset != 0) {
         off64_t offset = mFirstMoofOffset;
-        parseChunk(&offset);
+        return parseChunk(&offset);
     }
+    return OK;
 }
 
 MPEG4Source::~MPEG4Source() {
@@ -3780,9 +3799,30 @@
                     }
                     chunk_size = ntohl(hdr[0]);
                     chunk_type = ntohl(hdr[1]);
+                    if (chunk_size == 1) {
+                        // ISO/IEC 14496-12:2012, 8.8.4 Movie Fragment Box, moof is a Box
+                        // which is defined in 4.2 Object Structure.
+                        // When chunk_size==1, 8 bytes follows as "largesize".
+                        if (mDataSource->readAt(*offset + 8, &chunk_size, 8) < 8) {
+                            return ERROR_IO;
+                        }
+                        chunk_size = ntoh64(chunk_size);
+                        if (chunk_size < 16) {
+                            // The smallest valid chunk is 16 bytes long in this case.
+                            return ERROR_MALFORMED;
+                        }
+                    } else if (chunk_size == 0) {
+                        // next box extends to end of file.
+                    } else if (chunk_size < 8) {
+                        // The smallest valid chunk is 8 bytes long in this case.
+                        return ERROR_MALFORMED;
+                    }
+
                     if (chunk_type == FOURCC('m', 'o', 'o', 'f')) {
                         mNextMoofOffset = *offset;
                         break;
+                    } else if (chunk_size == 0) {
+                        break;
                     }
                     *offset += chunk_size;
                 }
@@ -4660,17 +4700,25 @@
                 totalOffset += se->mSize;
             }
             mCurrentMoofOffset = totalOffset;
+            mNextMoofOffset = -1;
             mCurrentSamples.clear();
             mCurrentSampleIndex = 0;
-            parseChunk(&totalOffset);
+            status_t err = parseChunk(&totalOffset);
+            if (err != OK) {
+                return err;
+            }
             mCurrentTime = totalTime * mTimescale / 1000000ll;
         } else {
             // without sidx boxes, we can only seek to 0
             mCurrentMoofOffset = mFirstMoofOffset;
+            mNextMoofOffset = -1;
             mCurrentSamples.clear();
             mCurrentSampleIndex = 0;
             off64_t tmp = mCurrentMoofOffset;
-            parseChunk(&tmp);
+            status_t err = parseChunk(&tmp);
+            if (err != OK) {
+                return err;
+            }
             mCurrentTime = 0;
         }
 
@@ -4699,7 +4747,10 @@
             mCurrentMoofOffset = nextMoof;
             mCurrentSamples.clear();
             mCurrentSampleIndex = 0;
-            parseChunk(&nextMoof);
+            status_t err = parseChunk(&nextMoof);
+            if (err != OK) {
+                return err;
+            }
             if (mCurrentSampleIndex >= mCurrentSamples.size()) {
                 return ERROR_END_OF_STREAM;
             }