linux-kernel - [PATCH 3/5] context_tracking: Restore preempted context state after preempt_schedule

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Fri,  1 Mar 2013 17:08:57 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Li Zhong <zhong@...ux.vnet.ibm.com>,
	Kevin Hilman <khilman@...aro.org>,
	Mats Liljegren <mats.liljegren@...a.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Namhyung Kim <namhyung.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 3/5] context_tracking: Restore preempted context state after preempt_schedule_irq()

>From the context tracking POV, preempt_schedule_irq() behaves pretty much
like an exception: It can be called anytime and schedule another task.

But currently it doesn't restore the context tracking state of the preempted
code on preempt_schedule_irq() return.

As a result, if preempt_schedule_irq() is called in the tiny frame between
user_enter() and the actual return to userspace, we resume userspace with
the wrong context tracking state.

Fix this by using exception_enter/exit() which are a perfect fit for this
kind of issue.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Li Zhong <zhong@...ux.vnet.ibm.com>
Cc: Kevin Hilman <khilman@...aro.org>
Cc: Mats Liljegren <mats.liljegren@...a.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Namhyung Kim <namhyung.kim@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/sched/core.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b7b03cd..db36e11 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3074,11 +3074,13 @@ EXPORT_SYMBOL(preempt_schedule);
 asmlinkage void __sched preempt_schedule_irq(void)
 {
 	struct thread_info *ti = current_thread_info();
+	enum ctx_state prev_state;
 
 	/* Catch callers which need to be fixed */
 	BUG_ON(ti->preempt_count || !irqs_disabled());
 
-	user_exit();
+	prev_state = exception_enter();
+
 	do {
 		add_preempt_count(PREEMPT_ACTIVE);
 		local_irq_enable();
@@ -3092,6 +3094,8 @@ asmlinkage void __sched preempt_schedule_irq(void)
 		 */
 		barrier();
 	} while (need_resched());
+
+	exception_exit(prev_state);
 }
 
 #endif /* CONFIG_PREEMPT */
-- 
1.7.5.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/