From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753214AbdBOW5N (ORCPT ); Wed, 15 Feb 2017 17:57:13 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:52412 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752557AbdBOWvR (ORCPT ); Wed, 15 Feb 2017 17:51:17 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Paolo Bonzini" , "Radim =?UTF-8?Q?Kr=C4=8Dm=C3=A1=C5=99?=" , "Ignacio Alvarado" Date: Wed, 15 Feb 2017 22:41:34 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 092/126] KVM: Disable irq while unregistering user notifier In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.85-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Ignacio Alvarado commit 1650b4ebc99da4c137bfbfc531be4a2405f951dd upstream. Function user_notifier_unregister should be called only once for each registered user notifier. Function kvm_arch_hardware_disable can be executed from an IPI context which could cause a race condition with a VCPU returning to user mode and attempting to unregister the notifier. Signed-off-by: Ignacio Alvarado Fixes: 18863bdd60f8 ("KVM: x86 shared msr infrastructure") Reviewed-by: Paolo Bonzini Signed-off-by: Radim Krčmář Signed-off-by: Ben Hutchings --- arch/x86/kvm/x86.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -172,7 +172,18 @@ static void kvm_on_user_return(struct us struct kvm_shared_msrs *locals = container_of(urn, struct kvm_shared_msrs, urn); struct kvm_shared_msr_values *values; + unsigned long flags; + /* + * Disabling irqs at this point since the following code could be + * interrupted and executed through kvm_arch_hardware_disable() + */ + local_irq_save(flags); + if (locals->registered) { + locals->registered = false; + user_return_notifier_unregister(urn); + } + local_irq_restore(flags); for (slot = 0; slot < shared_msrs_global.nr; ++slot) { values = &locals->values[slot]; if (values->host != values->curr) { @@ -180,8 +191,6 @@ static void kvm_on_user_return(struct us values->curr = values->host; } } - locals->registered = false; - user_return_notifier_unregister(urn); } static void shared_msr_update(unsigned slot, u32 msr)