Fix compile error with FORTIFY_SOURCE

You're gonna have a bad day if you attempt to read 3 bytes
into 1 byte.

(cherry picked from commit b4f59474493a0793375e723edbd0d29e55a8c581)

Change-Id: I6beea5631f30f4aa04ebbed10207f399187bf218
Merge tag 'android-4.4_r1' into kitkat

Android 4.4 Release 1.0