[PATCH v4 0/3] sched: Always check the integrity of the canary

[Aaron Tomlin <atomlin@redhat.com>]

Hi Peter,

Please let me know if this iteration is satisfactory. Thanks.


Currently in the event of a stack overrun a call to schedule()
does not check for this type of corruption. This corruption is
often silent and can go unnoticed. However once the corrupted
region is examined at a later stage, the outcome is undefined
and often results in a sporadic page fault which cannot be
handled.

The first patch adds a canary to init_task's end of stack.
While the second patch provides a helper to determine the
integrity of the canary. The third checks for a stack
overrun and takes appropriate action since the damage
is already done, there is no point in continuing.


Changes since v3:

 * Add Michael Ellerman's Acked-by to first patch
   (for powerpc)
 * Fix compiler error - Michael Ellerman
 * Set default Kconfig option to n - Michael Ellerman

Changes since v2:

 * Use BUG_ON in schedule_debug() - Peter Zijlstra
 * Use a more explicit function
   name for setting the canary - Chuck Ebbert

Changes since v1:

 * Rebased against v3.17-rc4
 * Add a canary to init_task - Oleg Nesterov
 * Fix various code formatting issues - Peter Zijlstra
 * Introduce Kconfig option - Peter Zijlstra

Aaron Tomlin (3):
  init/main.c: Give init_task a canary
  sched: Add helper for task stack page overrun checking
  sched: BUG when stack end location is over written

 arch/powerpc/mm/fault.c    |  5 +----
 arch/x86/mm/fault.c        |  5 +----
 include/linux/sched.h      |  4 ++++
 init/main.c                |  1 +
 kernel/fork.c              | 12 +++++++++---
 kernel/sched/core.c        |  3 +++
 kernel/trace/trace_stack.c |  4 +---
 lib/Kconfig.debug          | 12 ++++++++++++
 8 files changed, 32 insertions(+), 14 deletions(-)

-- 
1.9.3