DO NOT MERGE - MPEG4Extractor: Check mLastTrack before dereferencing.

Bug: 31449945
Change-Id: If2708b3006c22393e80a2557f93d8a71e4e7bf16
diff --git a/media/libstagefright/MPEG4Extractor.cpp b/media/libstagefright/MPEG4Extractor.cpp
index 8318848..eae35e7 100644
--- a/media/libstagefright/MPEG4Extractor.cpp
+++ b/media/libstagefright/MPEG4Extractor.cpp
@@ -861,6 +861,9 @@
                     }
                 }
 
+                if (mLastTrack == NULL) {
+                    return ERROR_MALFORMED;
+                }
                 mLastTrack->sampleTable = new SampleTable(mDataSource);
             }
 
@@ -957,6 +960,9 @@
             } else if (mHeaderTimescale == 0) {
                 ALOGW("ignoring edit list because timescale is 0");
             } else {
+                if (mLastTrack == NULL) {
+                    return ERROR_MALFORMED;
+                }
                 off64_t entriesoffset = data_offset + 8;
                 uint64_t segment_duration;
                 int64_t media_time;
@@ -1008,6 +1014,9 @@
 
         case FOURCC('f', 'r', 'm', 'a'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             uint32_t original_fourcc;
             if (mDataSource->readAt(data_offset, &original_fourcc, 4) < 4) {
                 return ERROR_IO;
@@ -1027,6 +1036,9 @@
 
         case FOURCC('t', 'e', 'n', 'c'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             if (chunk_size < 32) {
                 return ERROR_MALFORMED;
             }
@@ -1077,6 +1089,9 @@
 
         case FOURCC('t', 'k', 'h', 'd'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             status_t err;
             if ((err = parseTrackHeader(data_offset, chunk_data_size)) != OK) {
                 return err;
@@ -1122,6 +1137,9 @@
 
         case FOURCC('m', 'd', 'h', 'd'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             if (chunk_data_size < 4) {
                 return ERROR_MALFORMED;
             }
@@ -1230,6 +1248,9 @@
             uint32_t entry_count = U32_AT(&buffer[4]);
 
             if (entry_count > 1) {
+                if (mLastTrack == NULL) {
+                    return ERROR_MALFORMED;
+                }
                 // For 3GPP timed text, there could be multiple tx3g boxes contain
                 // multiple text display formats. These formats will be used to
                 // display the timed text.
@@ -1264,6 +1285,9 @@
         case FOURCC('s', 'a', 'm', 'r'):
         case FOURCC('s', 'a', 'w', 'b'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             uint8_t buffer[8 + 20];
             if (chunk_data_size < (ssize_t)sizeof(buffer)) {
                 // Basic AudioSampleEntry size.
@@ -1313,6 +1337,9 @@
         case FOURCC('h', '2', '6', '3'):
         case FOURCC('a', 'v', 'c', '1'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             mHasVideo = true;
 
             uint8_t buffer[78];
@@ -1365,6 +1392,9 @@
         case FOURCC('s', 't', 'c', 'o'):
         case FOURCC('c', 'o', '6', '4'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             status_t err =
                 mLastTrack->sampleTable->setChunkOffsetParams(
                         chunk_type, data_offset, chunk_data_size);
@@ -1379,6 +1409,9 @@
 
         case FOURCC('s', 't', 's', 'c'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             status_t err =
                 mLastTrack->sampleTable->setSampleToChunkParams(
                         data_offset, chunk_data_size);
@@ -1394,6 +1427,9 @@
         case FOURCC('s', 't', 's', 'z'):
         case FOURCC('s', 't', 'z', '2'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             status_t err =
                 mLastTrack->sampleTable->setSampleSizeParams(
                         chunk_type, data_offset, chunk_data_size);
@@ -1474,6 +1510,9 @@
 
         case FOURCC('s', 't', 't', 's'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             status_t err =
                 mLastTrack->sampleTable->setTimeToSampleParams(
                         data_offset, chunk_data_size);
@@ -1488,6 +1527,9 @@
 
         case FOURCC('c', 't', 't', 's'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             status_t err =
                 mLastTrack->sampleTable->setCompositionTimeToSampleParams(
                         data_offset, chunk_data_size);
@@ -1502,6 +1544,9 @@
 
         case FOURCC('s', 't', 's', 's'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             status_t err =
                 mLastTrack->sampleTable->setSyncSampleParams(
                         data_offset, chunk_data_size);
@@ -1551,6 +1596,9 @@
 
         case FOURCC('e', 's', 'd', 's'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             if (chunk_data_size < 4) {
                 return ERROR_MALFORMED;
             }
@@ -1594,6 +1642,9 @@
 
         case FOURCC('a', 'v', 'c', 'C'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             sp<ABuffer> buffer = new ABuffer(chunk_data_size);
 
             if (buffer->data() == NULL) {
@@ -1615,6 +1666,9 @@
 
         case FOURCC('d', '2', '6', '3'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             /*
              * d263 contains a fixed 7 bytes part:
              *   vendor - 4 bytes
@@ -1770,6 +1824,9 @@
 
         case FOURCC('t', 'x', '3', 'g'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             uint32_t type;
             const void *data;
             size_t size = 0;
@@ -1850,6 +1907,9 @@
 
         case FOURCC('s', 'i', 'd', 'x'):
         {
+            if (mLastTrack == NULL) {
+                return ERROR_MALFORMED;
+            }
             parseSegmentIndex(data_offset, chunk_data_size);
             *offset += chunk_size;
             return UNKNOWN_ERROR; // stop parsing after sidx
@@ -2212,6 +2272,9 @@
                     int32_t delay, padding;
                     if (sscanf(mLastCommentData,
                                " %*x %x %x %*x", &delay, &padding) == 2) {
+                        if (mLastTrack == NULL) {
+                            return ERROR_MALFORMED;
+                        }
                         mLastTrack->meta->setInt32(kKeyEncoderDelay, delay);
                         mLastTrack->meta->setInt32(kKeyEncoderPadding, padding);
                     }