linux-kernel - [PATCH 2.6.32-rc6] sched, kvm: fix race condition involving sched_in_preempt

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-next>] [day] [month] [year] [list]

Message-ID: <4AFD2801.7020900@kernel.org>
Date:	Fri, 13 Nov 2009 18:33:53 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Avi Kivity <avi@...hat.com>
CC:	lkml <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 2.6.32-rc6] sched, kvm: fix race condition involving sched_in_preempt_notifers

In finish_task_switch(), fire_sched_in_preempt_notifiers() is called
after finish_lock_switch().  However, depending on architecture,
preemption can be enabled after finish_lock_switch() which breaks the
semantics of preempt notifiers.  Move it before finish_arch_switch().
This also makes in notifiers symmetric to out notifiers in terms of
locking - now both are called under rq lock.

NOT_SIGNED_OFF_YET
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Avi Kivity <avi@...hat.com>
---
Avi, I think kvm should be fine with this but I haven't tested it.
Does this look okay to you?  If so, can you please route this through
kvm tree with my signoff?

Thanks.

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

Index: work/kernel/sched.c
===================================================================
--- work.orig/kernel/sched.c
+++ work/kernel/sched.c
@@ -2751,9 +2751,9 @@ static void finish_task_switch(struct rq
 	prev_state = prev->state;
 	finish_arch_switch(prev);
 	perf_event_task_sched_in(current, cpu_of(rq));
+	fire_sched_in_preempt_notifiers(current);
 	finish_lock_switch(rq, prev);
 
-	fire_sched_in_preempt_notifiers(current);
 	if (mm)
 		mmdrop(mm);
 	if (unlikely(prev_state == TASK_DEAD)) {
--
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/