[PATCH v2 0/5] bug: Provide toggle for BUG on data corruption

[Kees Cook]

This adds a CONFIG to trigger BUG()s when the kernel encounters
unexpected data structure integrity as currently detected with
CONFIG_DEBUG_LIST.

Specifically list operations have been a target for widening flaws to gain
"write anywhere" primitives for attackers, so this also consolidates the
debug checking to avoid code and check duplication (e.g. RCU list debug
was missing a check that got added to regular list debug). It also stops
manipulations when corruption is detected, since worsening the corruption
makes no sense. (Really, everyone should build with CONFIG_DEBUG_LIST
since the checks are so inexpensive.)

This is mostly a refactoring of similar code from PaX and Grsecurity,
along with MSM kernel changes by Stephen Boyd.

Along with the patches is a new lkdtm test to validate that setting
CONFIG_DEBUG_LIST actually does what is desired.

Thanks,

-Kees