linux-kernel - [PATCH 4.4 49/75] sched: panic on corrupted stack end

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Message-Id: <20160622223502.494297673@linuxfoundation.org>
Date:	Wed, 22 Jun 2016 15:41:11 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Jann Horn <jannh@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.4 49/75] sched: panic on corrupted stack end

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jann Horn <jannh@...gle.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@...gle.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3008,7 +3008,8 @@ 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())) {