Prevent integer issues in ID3::Iterator::findFrame

Integer overflows could occur a few places within findFrame. These can lead to
out-of-bounds reads and potentially infinite loops. Ensure that arithmetic does
not wrap around to prevent these behaviors.

Bug: 23285192
Change-Id: I72a61df7d5719d1d3f2bd0b37fba86f0f4bbedee
diff --git a/media/libstagefright/id3/ID3.cpp b/media/libstagefright/id3/ID3.cpp
index 751b810..5a490e9 100644
--- a/media/libstagefright/id3/ID3.cpp
+++ b/media/libstagefright/id3/ID3.cpp
@@ -659,6 +659,11 @@
 
             mFrameSize += 6;
 
+            // Prevent integer overflow in validation
+            if (SIZE_MAX - mOffset <= mFrameSize) {
+                return;
+            }
+
             if (mOffset + mFrameSize > mParent.mSize) {
                 ALOGV("partial frame at offset %d (size = %d, bytes-remaining = %d)",
                      mOffset, mFrameSize, mParent.mSize - mOffset - 6);
@@ -688,7 +693,7 @@
                 return;
             }
 
-            size_t baseSize;
+            size_t baseSize = 0;
             if (mParent.mVersion == ID3_V2_4) {
                 if (!ParseSyncsafeInteger(
                             &mParent.mData[mOffset + 4], &baseSize)) {
@@ -698,7 +703,21 @@
                 baseSize = U32_AT(&mParent.mData[mOffset + 4]);
             }
 
-            mFrameSize = 10 + baseSize;
+            if (baseSize == 0) {
+                return;
+            }
+
+            // Prevent integer overflow when adding
+            if (SIZE_MAX - 10 <= baseSize) {
+                return;
+            }
+
+            mFrameSize = 10 + baseSize; // add tag id, size field and flags
+
+            // Prevent integer overflow in validation
+            if (SIZE_MAX - mOffset <= mFrameSize) {
+                return;
+            }
 
             if (mOffset + mFrameSize > mParent.mSize) {
                 ALOGV("partial frame at offset %d (size = %d, bytes-remaining = %d)",