[PATCH 4.6 62/81] sched: panic on corrupted stack end

Greg Kroah-Hartman
2016-06-22T22:52:49Z

From: Jann Horn <jannh@google.com>

commit 29d6455178a09e1dc340380c582b13356227e8df upstream.

Until now, hitting this BUG_ON caused a recursive oops (because oops
handling involves do_exit(), which calls into the scheduler, which in
turn raises an oops), which caused stuff below the stack to be
overwritten until a panic happened (e.g. via an oops in interrupt
context, caused by the overwritten CPU index in the thread_info).

Just panic directly.

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/sched/core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3047,7 +3047,8 @@ static noinline void __schedule_bug(stru
static inline void schedule_debug(struct task_struct *prev)
{
#ifdef CONFIG_SCHED_STACK_END_CHECK
- BUG_ON(task_stack_end_corrupted(prev));
+ if (task_stack_end_corrupted(prev))
+ panic("corrupted stack end detected inside scheduler\n");
#endif

if (unlikely(in_atomic_preempt_off())) {