Verify presence of _FileAsset::getBuffer data

Rather than attempt to remove all users of Asset::getBuffer (which
includes AssetManager(1), aapt(1), and other places) and migrate  them
to use Asset::getIncFsBuffer, verify the presence of all the data in
the buffer before returning a raw pointer to the buffer data to
guarantee callers will not unexpectedly get a SIGBUS due to incremental
installation.

Bug: 179254882
Test: builds
Change-Id: I24fd9036bc53a8c23166b5471862ee542630fb56

1 files changed, 6 insertions, 1 deletions

diff --git a/libs/androidfw/Asset.cpp b/libs/androidfw/Asset.cpp
index 4fbe4a3efbdd..43a70c176a83 100644
--- a/libs/androidfw/Asset.cpp
+++ b/libs/androidfw/Asset.cpp
@@ -594,7 +594,12 @@ void _FileAsset::close(void)
  */
 const void* _FileAsset::getBuffer(bool aligned)
 {
-    return getIncFsBuffer(aligned).unsafe_ptr();
+    auto buffer = getIncFsBuffer(aligned);
+    if (mBuf != NULL)
+        return mBuf;
+    if (!buffer.convert<uint8_t>().verify(mLength))
+        return NULL;
+    return buffer.unsafe_ptr();
 }
 
 incfs::map_ptr<void> _FileAsset::getIncFsBuffer(bool aligned)