That is mostly true, you can still hose them by overrunning a buffer into their memory accounting areas, but I have checked that already...
To make the problem even more strange it seems to be limited to certain hardware. Running SLES, RHEL, Gentoo, Debian, or Ubuntu on x86 works fine, running RHEL or SLES on an IBM POWER 720 works fine, but it breaks on any distro running on an IBM POWER Blade JS20.