[CVE-2012-0957] kernel: uts: stack memory leak in UNAME26

[Luis Henriques]

When using the UNAME26 personality, the uname() syscall will leak kernel
stack contents.  There's a simple test case for this issue here:

 http://bugs.launchpad.net/bugs/1060521

Following this email, there are three patches.  The first two contain the
two commits with the fix for Quantal.  Precise already contains one of the
commits (from the stable updates), thus the third patch contains the
missing commit to Precise.  All these are clean cherry-picks.