Prevent integer overflow when calculating buffer resizes

Make sure that we don't go haywire if an exponential buffer growth
operation winds up wrapping integer range.  Along the way, fix a
bookkeeping bug in BufferedTextOutput that would cause it to keep
spuriously realloc()ing on every append().

Bug 20674694

Change-Id: Ia845b7de36b90672a151a918ffc26c7da68e20a2

1 files changed, 3 insertions, 1 deletions

diff --git a/libs/binder/Parcel.cpp b/libs/binder/Parcel.cpp
index 2ebf617..31667d9 100644
--- a/libs/binder/Parcel.cpp
+++ b/libs/binder/Parcel.cpp
@@ -484,7 +484,8 @@ status_t Parcel::appendFrom(const Parcel *parcel, size_t offset, size_t len)
     if (numObjects > 0) {
         // grow objects
         if (mObjectsCapacity < mObjectsSize + numObjects) {
-            int newSize = ((mObjectsSize + numObjects)*3)/2;
+            size_t newSize = ((mObjectsSize + numObjects)*3)/2;
+            if (newSize < mObjectsSize) return NO_MEMORY;   // overflow
             binder_size_t *objects =
                 (binder_size_t*)realloc(mObjects, newSize*sizeof(binder_size_t));
             if (objects == (binder_size_t*)0) {
@@ -1038,6 +1039,7 @@ restart_write:
     }
     if (!enoughObjects) {
         size_t newSize = ((mObjectsSize+2)*3)/2;
+        if (newSize < mObjectsSize) return NO_MEMORY;   // overflow
         binder_size_t* objects = (binder_size_t*)realloc(mObjects, newSize*sizeof(binder_size_t));
         if (objects == NULL) return NO_MEMORY;
         mObjects = objects;