From: Jann Horn <jannh@google.com>
Date: Wed, 1 Jun 2016 09:55:07 +0000 (+0200)
Subject: sched: panic on corrupted stack end
X-Git-Tag: firefly_0821_release~176^2~4^2~40^2~33
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=c08b1a593a042ae01e788ec5504bee2cfc83e1f2;p=firefly-linux-kernel-4.4.55.git

sched: panic on corrupted stack end

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>
---

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 55bebf924946..6c0cdb5a73f8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3008,7 +3008,8 @@ static noinline void __schedule_bug(struct task_struct *prev)
 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())) {