From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755237AbaITGnO (ORCPT ); Sat, 20 Sep 2014 02:43:14 -0400 Received: from terminus.zytor.com ([198.137.202.10]:36879 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752000AbaITGnM (ORCPT ); Sat, 20 Sep 2014 02:43:12 -0400 Date: Fri, 19 Sep 2014 23:42:37 -0700 From: tip-bot for Chuck Ebbert Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, cebbert.lkml@gmail.com, james.hogan@imgtec.com, atomlin@redhat.com, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, cebbert.lkml@gmail.com, james.hogan@imgtec.com, tglx@linutronix.de, atomlin@redhat.com In-Reply-To: <20140919093505.62681e43@as> References: <20140919093505.62681e43@as> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched: Fix end_of_stack() and location of stack canary for architectures using CONFIG_STACK_GROWSUP Git-Commit-ID: a3215fb47c7ecb814dc16815245db4f375841268 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: a3215fb47c7ecb814dc16815245db4f375841268 Gitweb: http://git.kernel.org/tip/a3215fb47c7ecb814dc16815245db4f375841268 Author: Chuck Ebbert AuthorDate: Fri, 19 Sep 2014 09:35:05 -0500 Committer: Ingo Molnar CommitDate: Sat, 20 Sep 2014 08:38:16 +0200 sched: Fix end_of_stack() and location of stack canary for architectures using CONFIG_STACK_GROWSUP Aaron Tomlin recently posted patches to enable checking the stack canary on every task switch: http://lkml.org/lkml/2014/9/12/293 Looking at the canary code, I realized that every arch (except ia64, which adds some space for register spill above the stack) shares a definition of end_of_stack() that makes it the first long after the threadinfo. For stacks that grow down, this low address is correct because the stack starts at the end of the thread area and grows toward lower addresses. However, for stacks that grow up, toward higher addresses, this is wrong. (The stack actually grows away from the canary.) On these archs end_of_stack() should return the address of the last long, at the highest possible address for the stack. Signed-off-by: Chuck Ebbert Tested-by: James Hogan [metag] Acked-by: James Hogan Acked-by: Aaron Tomlin Link: http://lkml.kernel.org/r/20140919093505.62681e43@as [ Added comments to end_of_stack(). ] Signed-off-by: Ingo Molnar --- include/linux/sched.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index 5c2c885..0e20a24 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2608,9 +2608,22 @@ static inline void setup_thread_stack(struct task_struct *p, struct task_struct task_thread_info(p)->task = p; } +/* + * Return the address of the first long before (or after, + * depending on the architecture's default stack growth + * direction) * a task's task_info structure, which is the + * kernel stack's last usable spot. + * + * This is the point of no return, if the stack grows + * beyond that position, we corrupt the task's state. + */ static inline unsigned long *end_of_stack(struct task_struct *p) { +#ifdef CONFIG_STACK_GROWSUP + return (unsigned long *)((unsigned long)task_thread_info(p) + THREAD_SIZE) - 1; +#else return (unsigned long *)(task_thread_info(p) + 1); +#endif } #endif