Fix timedtext parsing

Add bounds checking and fix other bugs.

Bug: 23284974
Bug: 23541506
Bug: 23542351
Bug: 23542352
Change-Id: I53551efdf109ce1833e0c361efaf4cee7a851023

2 files changed, 377 insertions, 254 deletions

diff --git a/media/libstagefright/timedtext/TextDescriptions.cpp b/media/libstagefright/timedtext/TextDescriptions.cpp
index f9c1fe0..c762a74 100644
--- a/media/libstagefright/timedtext/TextDescriptions.cpp
+++ b/media/libstagefright/timedtext/TextDescriptions.cpp
@@ -30,9 +30,9 @@ status_t TextDescriptions::getParcelOfDescriptions(
 
     if (flags & IN_BAND_TEXT_3GPP) {
         if (flags & GLOBAL_DESCRIPTIONS) {
-            return extract3GPPGlobalDescriptions(data, size, parcel, 0);
+            return extract3GPPGlobalDescriptions(data, size, parcel);
         } else if (flags & LOCAL_DESCRIPTIONS) {
-            return extract3GPPLocalDescriptions(data, size, timeMs, parcel, 0);
+            return extract3GPPLocalDescriptions(data, size, timeMs, parcel);
         }
     } else if (flags & OUT_OF_BAND_TEXT_SRT) {
         if (flags & LOCAL_DESCRIPTIONS) {
@@ -69,314 +69,437 @@ status_t TextDescriptions::extractSRTLocalDescriptions(
 // styles, and 'krok' box contains karaoke timing and positions.
 status_t TextDescriptions::extract3GPPLocalDescriptions(
         const uint8_t *data, ssize_t size,
-        int timeMs, Parcel *parcel, int depth) {
-    if (depth == 0) {
-        parcel->writeInt32(KEY_LOCAL_SETTING);
-
-        // write start time to display this text sample
-        parcel->writeInt32(KEY_START_TIME);
-        parcel->writeInt32(timeMs);
-
-        ssize_t textLen = (*data) << 8 | (*(data + 1));
-
-        // write text sample length and text sample itself
-        parcel->writeInt32(KEY_STRUCT_TEXT);
-        parcel->writeInt32(textLen);
-        parcel->writeInt32(textLen);
-        parcel->write(data + 2, textLen);
-
-        if (size > textLen) {
-            data += (textLen + 2);
-            size -= (textLen + 2);
-        } else {
-            return OK;
-        }
+        int timeMs, Parcel *parcel) {
+
+    parcel->writeInt32(KEY_LOCAL_SETTING);
+
+    // write start time to display this text sample
+    parcel->writeInt32(KEY_START_TIME);
+    parcel->writeInt32(timeMs);
+
+    if (size < 2) {
+        return OK;
     }
+    ssize_t textLen = (*data) << 8 | (*(data + 1));
 
-    const uint8_t *tmpData = data;
-    ssize_t chunkSize = U32_AT(tmpData);
-    uint32_t chunkType = U32_AT(tmpData + 4);
+    if (size < textLen + 2) {
+        return OK;
+    }
 
-    if (chunkSize <= 0) {
+    // write text sample length and text sample itself
+    parcel->writeInt32(KEY_STRUCT_TEXT);
+    parcel->writeInt32(textLen);
+    parcel->writeInt32(textLen);
+    parcel->write(data + 2, textLen);
+
+    if (size > textLen + 2) {
+        data += (textLen + 2);
+        size -= (textLen + 2);
+    } else {
         return OK;
     }
 
-    tmpData += 8;
+    while (size >= 8) {
+        const uint8_t *tmpData = data;
+        ssize_t chunkSize = U32_AT(tmpData);      // size includes size and type
+        uint32_t chunkType = U32_AT(tmpData + 4);
 
-    switch(chunkType) {
-        // 'styl' box specifies the style of the text.
-        case FOURCC('s', 't', 'y', 'l'):
-        {
-            uint16_t count = U16_AT(tmpData);
+        if (chunkSize <= 8 || chunkSize > size) {
+            return OK;
+        }
 
-            tmpData += 2;
+        size_t remaining = chunkSize - 8;
 
-            for (int i = 0; i < count; i++) {
-                parcel->writeInt32(KEY_STRUCT_STYLE_LIST);
-                parcel->writeInt32(KEY_START_CHAR);
-                parcel->writeInt32(U16_AT(tmpData));
+        tmpData += 8;
 
-                parcel->writeInt32(KEY_END_CHAR);
-                parcel->writeInt32(U16_AT(tmpData + 2));
+        switch(chunkType) {
+            // 'styl' box specifies the style of the text.
+            case FOURCC('s', 't', 'y', 'l'):
+            {
+                if (remaining < 2) {
+                    return OK;
+                }
+                size_t dataPos = parcel->dataPosition();
+                uint16_t count = U16_AT(tmpData);
 
-                parcel->writeInt32(KEY_FONT_ID);
-                parcel->writeInt32(U16_AT(tmpData + 4));
+                tmpData += 2;
+                remaining -= 2;
 
-                parcel->writeInt32(KEY_STYLE_FLAGS);
-                parcel->writeInt32(*(tmpData + 6));
+                for (int i = 0; i < count; i++) {
+                    if (remaining < 12) {
+                        // roll back
+                        parcel->setDataPosition(dataPos);
+                        return OK;
+                    }
+                    parcel->writeInt32(KEY_STRUCT_STYLE_LIST);
+                    parcel->writeInt32(KEY_START_CHAR);
+                    parcel->writeInt32(U16_AT(tmpData));
 
-                parcel->writeInt32(KEY_FONT_SIZE);
-                parcel->writeInt32(*(tmpData + 7));
+                    parcel->writeInt32(KEY_END_CHAR);
+                    parcel->writeInt32(U16_AT(tmpData + 2));
 
-                parcel->writeInt32(KEY_TEXT_COLOR_RGBA);
-                uint32_t rgba = *(tmpData + 8) << 24 | *(tmpData + 9) << 16
-                    | *(tmpData + 10) << 8 | *(tmpData + 11);
-                parcel->writeInt32(rgba);
+                    parcel->writeInt32(KEY_FONT_ID);
+                    parcel->writeInt32(U16_AT(tmpData + 4));
 
-                tmpData += 12;
+                    parcel->writeInt32(KEY_STYLE_FLAGS);
+                    parcel->writeInt32(*(tmpData + 6));
+
+                    parcel->writeInt32(KEY_FONT_SIZE);
+                    parcel->writeInt32(*(tmpData + 7));
+
+                    parcel->writeInt32(KEY_TEXT_COLOR_RGBA);
+                    uint32_t rgba = *(tmpData + 8) << 24 | *(tmpData + 9) << 16
+                        | *(tmpData + 10) << 8 | *(tmpData + 11);
+                    parcel->writeInt32(rgba);
+
+                    tmpData += 12;
+                    remaining -= 12;
+                }
+
+                break;
+            }
+            // 'krok' box. The number of highlight events is specified, and each
+            // event is specified by a starting and ending char offset and an end
+            // time for the event.
+            case FOURCC('k', 'r', 'o', 'k'):
+            {
+                if (remaining < 6) {
+                    return OK;
+                }
+                size_t dataPos = parcel->dataPosition();
+
+                parcel->writeInt32(KEY_STRUCT_KARAOKE_LIST);
+
+                int startTime = U32_AT(tmpData);
+                uint16_t count = U16_AT(tmpData + 4);
+                parcel->writeInt32(count);
+
+                tmpData += 6;
+                remaining -= 6;
+                int lastEndTime = 0;
+
+                for (int i = 0; i < count; i++) {
+                    if (remaining < 8) {
+                        // roll back
+                        parcel->setDataPosition(dataPos);
+                        return OK;
+                    }
+                    parcel->writeInt32(startTime + lastEndTime);
+
+                    lastEndTime = U32_AT(tmpData);
+                    parcel->writeInt32(lastEndTime);
+
+                    parcel->writeInt32(U16_AT(tmpData + 4));
+                    parcel->writeInt32(U16_AT(tmpData + 6));
+
+                    tmpData += 8;
+                    remaining -= 8;
+                }
+
+                break;
             }
+            // 'hlit' box specifies highlighted text
+            case FOURCC('h', 'l', 'i', 't'):
+            {
+                if (remaining < 4) {
+                    return OK;
+                }
 
-            break;
-        }
-        // 'krok' box. The number of highlight events is specified, and each
-        // event is specified by a starting and ending char offset and an end
-        // time for the event.
-        case FOURCC('k', 'r', 'o', 'k'):
-        {
+                parcel->writeInt32(KEY_STRUCT_HIGHLIGHT_LIST);
 
-            parcel->writeInt32(KEY_STRUCT_KARAOKE_LIST);
+                // the start char offset to highlight
+                parcel->writeInt32(U16_AT(tmpData));
+                // the last char offset to highlight
+                parcel->writeInt32(U16_AT(tmpData + 2));
 
-            int startTime = U32_AT(tmpData);
-            uint16_t count = U16_AT(tmpData + 4);
-            parcel->writeInt32(count);
+                tmpData += 4;
+                remaining -= 4;
+                break;
+            }
+            // 'hclr' box specifies the RGBA color: 8 bits each of
+            // red, green, blue, and an alpha(transparency) value
+            case FOURCC('h', 'c', 'l', 'r'):
+            {
+                if (remaining < 4) {
+                    return OK;
+                }
+                parcel->writeInt32(KEY_HIGHLIGHT_COLOR_RGBA);
+
+                uint32_t rgba = *(tmpData) << 24 | *(tmpData + 1) << 16
+                    | *(tmpData + 2) << 8 | *(tmpData + 3);
+                parcel->writeInt32(rgba);
+
+                tmpData += 4;
+                remaining -= 4;
+                break;
+            }
+            // 'dlay' box specifies a delay after a scroll in and/or
+            // before scroll out.
+            case FOURCC('d', 'l', 'a', 'y'):
+            {
+                if (remaining < 4) {
+                    return OK;
+                }
+                parcel->writeInt32(KEY_SCROLL_DELAY);
+
+                uint32_t delay = *(tmpData) << 24 | *(tmpData + 1) << 16
+                    | *(tmpData + 2) << 8 | *(tmpData + 3);
+                parcel->writeInt32(delay);
+
+                tmpData += 4;
+                remaining -= 4;
+                break;
+            }
+            // 'href' box for hyper text link
+            case FOURCC('h', 'r', 'e', 'f'):
+            {
+                if (remaining < 5) {
+                    return OK;
+                }
 
-            tmpData += 6;
-            int lastEndTime = 0;
+                size_t dataPos = parcel->dataPosition();
 
-            for (int i = 0; i < count; i++) {
-                parcel->writeInt32(startTime + lastEndTime);
+                parcel->writeInt32(KEY_STRUCT_HYPER_TEXT_LIST);
 
-                lastEndTime = U32_AT(tmpData);
-                parcel->writeInt32(lastEndTime);
+                // the start offset of the text to be linked
+                parcel->writeInt32(U16_AT(tmpData));
+                // the end offset of the text
+                parcel->writeInt32(U16_AT(tmpData + 2));
 
+                // the number of bytes in the following URL
+                size_t len = *(tmpData + 4);
+                parcel->writeInt32(len);
+
+                remaining -= 5;
+
+                if (remaining  < len) {
+                    parcel->setDataPosition(dataPos);
+                    return OK;
+                }
+                // the linked-to URL
+                parcel->writeInt32(len);
+                parcel->write(tmpData + 5, len);
+
+                tmpData += (5 + len);
+                remaining -= len;
+
+                if (remaining  < 1) {
+                    parcel->setDataPosition(dataPos);
+                    return OK;
+                }
+
+                // the number of bytes in the following "alt" string
+                len = *tmpData;
+                parcel->writeInt32(len);
+
+                tmpData += 1;
+                remaining -= 1;
+                if (remaining  < len) {
+                    parcel->setDataPosition(dataPos);
+                    return OK;
+                }
+
+                // an "alt" string for user display
+                parcel->writeInt32(len);
+                parcel->write(tmpData, len);
+
+                tmpData += 1;
+                remaining -= 1;
+                break;
+            }
+            // 'tbox' box to indicate the position of the text with values
+            // of top, left, bottom and right
+            case FOURCC('t', 'b', 'o', 'x'):
+            {
+                if (remaining < 8) {
+                    return OK;
+                }
+                parcel->writeInt32(KEY_STRUCT_TEXT_POS);
+                parcel->writeInt32(U16_AT(tmpData));
+                parcel->writeInt32(U16_AT(tmpData + 2));
                 parcel->writeInt32(U16_AT(tmpData + 4));
                 parcel->writeInt32(U16_AT(tmpData + 6));
 
                 tmpData += 8;
+                remaining -= 8;
+                break;
             }
+            // 'blnk' to specify the char range to be blinked
+            case FOURCC('b', 'l', 'n', 'k'):
+            {
+                if (remaining < 4) {
+                    return OK;
+                }
 
-            break;
-        }
-        // 'hlit' box specifies highlighted text
-        case FOURCC('h', 'l', 'i', 't'):
-        {
-            parcel->writeInt32(KEY_STRUCT_HIGHLIGHT_LIST);
+                parcel->writeInt32(KEY_STRUCT_BLINKING_TEXT_LIST);
 
-            // the start char offset to highlight
-            parcel->writeInt32(U16_AT(tmpData));
-            // the last char offset to highlight
-            parcel->writeInt32(U16_AT(tmpData + 2));
+                // start char offset
+                parcel->writeInt32(U16_AT(tmpData));
+                // end char offset
+                parcel->writeInt32(U16_AT(tmpData + 2));
 
-            break;
+                tmpData += 4;
+                remaining -= 4;
+                break;
+            }
+            // 'twrp' box specifies text wrap behavior. If the value if 0x00,
+            // then no wrap. If it's 0x01, then automatic 'soft' wrap is enabled.
+            // 0x02-0xff are reserved.
+            case FOURCC('t', 'w', 'r', 'p'):
+            {
+                if (remaining < 1) {
+                    return OK;
+                }
+                parcel->writeInt32(KEY_WRAP_TEXT);
+                parcel->writeInt32(*tmpData);
+
+                tmpData += 1;
+                remaining -= 1;
+                break;
+            }
+            default:
+            {
+                break;
+            }
         }
-        // 'hclr' box specifies the RGBA color: 8 bits each of
-        // red, green, blue, and an alpha(transparency) value
-        case FOURCC('h', 'c', 'l', 'r'):
-        {
-            parcel->writeInt32(KEY_HIGHLIGHT_COLOR_RGBA);
 
-            uint32_t rgba = *(tmpData) << 24 | *(tmpData + 1) << 16
-                | *(tmpData + 2) << 8 | *(tmpData + 3);
-            parcel->writeInt32(rgba);
+        data += chunkSize;
+        size -= chunkSize;
+    }
+
+    return OK;
+}
 
-            break;
-        }
-        // 'dlay' box specifies a delay after a scroll in and/or
-        // before scroll out.
-        case FOURCC('d', 'l', 'a', 'y'):
-        {
-            parcel->writeInt32(KEY_SCROLL_DELAY);
+// To extract box 'tx3g' defined in 3GPP TS 26.245, and store it in a Parcel
+status_t TextDescriptions::extract3GPPGlobalDescriptions(
+        const uint8_t *data, ssize_t size, Parcel *parcel) {
+
+    parcel->writeInt32(KEY_GLOBAL_SETTING);
 
-            uint32_t delay = *(tmpData) << 24 | *(tmpData + 1) << 16
-                | *(tmpData + 2) << 8 | *(tmpData + 3);
-            parcel->writeInt32(delay);
+    while (size >= 8) {
+        ssize_t chunkSize = U32_AT(data);
+        uint32_t chunkType = U32_AT(data + 4);
+        const uint8_t *tmpData = data;
+        tmpData += 8;
+        size_t remaining = size - 8;
 
-            break;
+        if (size < chunkSize) {
+            return OK;
         }
-        // 'href' box for hyper text link
-        case FOURCC('h', 'r', 'e', 'f'):
-        {
-            parcel->writeInt32(KEY_STRUCT_HYPER_TEXT_LIST);
+        switch(chunkType) {
+            case FOURCC('t', 'x', '3', 'g'):
+            {
+                if (remaining < 18) { // 8 just below, and another 10 a little further down
+                    return OK;
+                }
+                tmpData += 8; // skip the first 8 bytes
+                remaining -=8;
+                parcel->writeInt32(KEY_DISPLAY_FLAGS);
+                parcel->writeInt32(U32_AT(tmpData));
+
+                parcel->writeInt32(KEY_STRUCT_JUSTIFICATION);
+                parcel->writeInt32(tmpData[4]);
+                parcel->writeInt32(tmpData[5]);
+
+                parcel->writeInt32(KEY_BACKGROUND_COLOR_RGBA);
+                uint32_t rgba = *(tmpData + 6) << 24 | *(tmpData + 7) << 16
+                    | *(tmpData + 8) << 8 | *(tmpData + 9);
+                parcel->writeInt32(rgba);
 
-            // the start offset of the text to be linked
-            parcel->writeInt32(U16_AT(tmpData));
-            // the end offset of the text
-            parcel->writeInt32(U16_AT(tmpData + 2));
+                tmpData += 10;
+                remaining -= 10;
 
-            // the number of bytes in the following URL
-            int len = *(tmpData + 4);
-            parcel->writeInt32(len);
+                if (remaining < 8) {
+                    return OK;
+                }
+                parcel->writeInt32(KEY_STRUCT_TEXT_POS);
+                parcel->writeInt32(U16_AT(tmpData));
+                parcel->writeInt32(U16_AT(tmpData + 2));
+                parcel->writeInt32(U16_AT(tmpData + 4));
+                parcel->writeInt32(U16_AT(tmpData + 6));
 
-            // the linked-to URL
-            parcel->writeInt32(len);
-            parcel->write(tmpData + 5, len);
+                tmpData += 8;
+                remaining -= 8;
 
-            tmpData += (5 + len);
+                if (remaining < 12) {
+                    return OK;
+                }
+                parcel->writeInt32(KEY_STRUCT_STYLE_LIST);
+                parcel->writeInt32(KEY_START_CHAR);
+                parcel->writeInt32(U16_AT(tmpData));
 
-            // the number of bytes in the following "alt" string
-            len = *tmpData;
-            parcel->writeInt32(len);
+                parcel->writeInt32(KEY_END_CHAR);
+                parcel->writeInt32(U16_AT(tmpData + 2));
 
-            // an "alt" string for user display
-            parcel->writeInt32(len);
-            parcel->write(tmpData + 1, len);
+                parcel->writeInt32(KEY_FONT_ID);
+                parcel->writeInt32(U16_AT(tmpData + 4));
 
-            break;
-        }
-        // 'tbox' box to indicate the position of the text with values
-        // of top, left, bottom and right
-        case FOURCC('t', 'b', 'o', 'x'):
-        {
-            parcel->writeInt32(KEY_STRUCT_TEXT_POS);
-            parcel->writeInt32(U16_AT(tmpData));
-            parcel->writeInt32(U16_AT(tmpData + 2));
-            parcel->writeInt32(U16_AT(tmpData + 4));
-            parcel->writeInt32(U16_AT(tmpData + 6));
-
-            break;
-        }
-        // 'blnk' to specify the char range to be blinked
-        case FOURCC('b', 'l', 'n', 'k'):
-        {
-            parcel->writeInt32(KEY_STRUCT_BLINKING_TEXT_LIST);
+                parcel->writeInt32(KEY_STYLE_FLAGS);
+                parcel->writeInt32(*(tmpData + 6));
 
-            // start char offset
-            parcel->writeInt32(U16_AT(tmpData));
-            // end char offset
-            parcel->writeInt32(U16_AT(tmpData + 2));
+                parcel->writeInt32(KEY_FONT_SIZE);
+                parcel->writeInt32(*(tmpData + 7));
 
-            break;
-        }
-        // 'twrp' box specifies text wrap behavior. If the value if 0x00,
-        // then no wrap. If it's 0x01, then automatic 'soft' wrap is enabled.
-        // 0x02-0xff are reserved.
-        case FOURCC('t', 'w', 'r', 'p'):
-        {
-            parcel->writeInt32(KEY_WRAP_TEXT);
-            parcel->writeInt32(*tmpData);
-
-            break;
-        }
-        default:
-        {
-            break;
-        }
-    }
+                parcel->writeInt32(KEY_TEXT_COLOR_RGBA);
+                rgba = *(tmpData + 8) << 24 | *(tmpData + 9) << 16
+                    | *(tmpData + 10) << 8 | *(tmpData + 11);
+                parcel->writeInt32(rgba);
 
-    if (size > chunkSize) {
-        data += chunkSize;
-        size -= chunkSize;
-        // continue to parse next box
-        return extract3GPPLocalDescriptions(data, size, 0, parcel, 1);
-    }
+                tmpData += 12;
+                remaining -= 12;
 
-    return OK;
-}
+                if (remaining < 2) {
+                    return OK;
+                }
 
-// To extract box 'tx3g' defined in 3GPP TS 26.245, and store it in a Parcel
-status_t TextDescriptions::extract3GPPGlobalDescriptions(
-        const uint8_t *data, ssize_t size, Parcel *parcel, int depth) {
+                size_t dataPos = parcel->dataPosition();
 
-    ssize_t chunkSize = U32_AT(data);
-    uint32_t chunkType = U32_AT(data + 4);
-    const uint8_t *tmpData = data;
-    tmpData += 8;
+                parcel->writeInt32(KEY_STRUCT_FONT_LIST);
+                uint16_t count = U16_AT(tmpData);
+                parcel->writeInt32(count);
 
-    if (size < chunkSize) {
-        return OK;
-    }
+                tmpData += 2;
+                remaining -= 2;
 
-    if (depth == 0) {
-        parcel->writeInt32(KEY_GLOBAL_SETTING);
-    }
-    switch(chunkType) {
-        case FOURCC('t', 'x', '3', 'g'):
-        {
-            tmpData += 8; // skip the first 8 bytes
-            parcel->writeInt32(KEY_DISPLAY_FLAGS);
-            parcel->writeInt32(U32_AT(tmpData));
-
-            parcel->writeInt32(KEY_STRUCT_JUSTIFICATION);
-            parcel->writeInt32(tmpData[4]);
-            parcel->writeInt32(tmpData[5]);
-
-            parcel->writeInt32(KEY_BACKGROUND_COLOR_RGBA);
-            uint32_t rgba = *(tmpData + 6) << 24 | *(tmpData + 7) << 16
-                | *(tmpData + 8) << 8 | *(tmpData + 9);
-            parcel->writeInt32(rgba);
-
-            tmpData += 10;
-            parcel->writeInt32(KEY_STRUCT_TEXT_POS);
-            parcel->writeInt32(U16_AT(tmpData));
-            parcel->writeInt32(U16_AT(tmpData + 2));
-            parcel->writeInt32(U16_AT(tmpData + 4));
-            parcel->writeInt32(U16_AT(tmpData + 6));
-
-            tmpData += 8;
-            parcel->writeInt32(KEY_STRUCT_STYLE_LIST);
-            parcel->writeInt32(KEY_START_CHAR);
-            parcel->writeInt32(U16_AT(tmpData));
-
-            parcel->writeInt32(KEY_END_CHAR);
-            parcel->writeInt32(U16_AT(tmpData + 2));
-
-            parcel->writeInt32(KEY_FONT_ID);
-            parcel->writeInt32(U16_AT(tmpData + 4));
-
-            parcel->writeInt32(KEY_STYLE_FLAGS);
-            parcel->writeInt32(*(tmpData + 6));
-
-            parcel->writeInt32(KEY_FONT_SIZE);
-            parcel->writeInt32(*(tmpData + 7));
-
-            parcel->writeInt32(KEY_TEXT_COLOR_RGBA);
-            rgba = *(tmpData + 8) << 24 | *(tmpData + 9) << 16
-                | *(tmpData + 10) << 8 | *(tmpData + 11);
-            parcel->writeInt32(rgba);
-
-            tmpData += 12;
-            parcel->writeInt32(KEY_STRUCT_FONT_LIST);
-            uint16_t count = U16_AT(tmpData);
-            parcel->writeInt32(count);
-
-            tmpData += 2;
-            for (int i = 0; i < count; i++) {
-                // font ID
-                parcel->writeInt32(U16_AT(tmpData));
+                for (int i = 0; i < count; i++) {
+                    if (remaining < 3) {
+                        // roll back
+                        parcel->setDataPosition(dataPos);
+                        return OK;
+                    }
+                    // font ID
+                    parcel->writeInt32(U16_AT(tmpData));
 
-                // font name length
-                parcel->writeInt32(*(tmpData + 2));
+                    // font name length
+                    parcel->writeInt32(*(tmpData + 2));
 
-                int len = *(tmpData + 2);
+                    size_t len = *(tmpData + 2);
 
-                parcel->write(tmpData + 3, len);
-                tmpData += 3 + len;
-            }
+                    tmpData += 3;
+                    remaining -= 3;
 
-            break;
-        }
-        default:
-        {
-            break;
-        }
-    }
+                    if (remaining < len) {
+                        // roll back
+                        parcel->setDataPosition(dataPos);
+                        return OK;
+                    }
 
-    data += chunkSize;
-    size -= chunkSize;
+                    parcel->write(tmpData, len);
+                    tmpData += len;
+                    remaining -= len;
+                }
 
-    if (size > 0) {
-        // continue to extract next 'tx3g'
-        return extract3GPPGlobalDescriptions(data, size, parcel, 1);
+                // there is a "DisparityBox" after this according to the spec, but we ignore it
+                break;
+            }
+            default:
+            {
+                break;
+            }
+        }
+
+        data += chunkSize;
+        size -= chunkSize;
     }
 
     return OK;
diff --git a/media/libstagefright/timedtext/TextDescriptions.h b/media/libstagefright/timedtext/TextDescriptions.h
index 0144917..bf67f3f 100644
--- a/media/libstagefright/timedtext/TextDescriptions.h
+++ b/media/libstagefright/timedtext/TextDescriptions.h
@@ -72,10 +72,10 @@ private:
             int timeMs, Parcel *parcel);
     static status_t extract3GPPGlobalDescriptions(
             const uint8_t *data, ssize_t size,
-            Parcel *parcel, int depth);
+            Parcel *parcel);
     static status_t extract3GPPLocalDescriptions(
             const uint8_t *data, ssize_t size,
-            int timeMs, Parcel *parcel, int depth);
+            int timeMs, Parcel *parcel);
 
     DISALLOW_EVIL_CONSTRUCTORS(TextDescriptions);
 };