From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932978Ab0GAU6i (ORCPT ); Thu, 1 Jul 2010 16:58:38 -0400 Received: from kroah.org ([198.145.64.141]:47982 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932901Ab0GAUvf (ORCPT ); Thu, 1 Jul 2010 16:51:35 -0400 X-Mailbox-Line: From gregkh@clark.site Thu Jul 1 10:34:39 2010 Message-Id: <20100701173439.876167191@clark.site> User-Agent: quilt/0.48-10.1 Date: Thu, 01 Jul 2010 10:35:41 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Glauber Costa , Avi Kivity Subject: [patch 155/164] KVM: Fix wallclock version writing race In-Reply-To: <20100701175152.GA2135@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.33-stable review patch. If anyone has any objections, please let me know. ------------------ From: Avi Kivity Wallclock writing uses an unprotected global variable to hold the version; this can cause one guest to interfere with another if both write their wallclock at the same time. Acked-by: Glauber Costa Signed-off-by: Avi Kivity Signed-off-by: Greg Kroah-Hartman (cherry picked from commit 9ed3c444ab8987c7b219173a2f7807e3f71e234e) --- arch/x86/kvm/x86.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -641,14 +641,22 @@ static int do_set_msr(struct kvm_vcpu *v static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock) { - static int version; + int version; + int r; struct pvclock_wall_clock wc; struct timespec boot; if (!wall_clock) return; - version++; + r = kvm_read_guest(kvm, wall_clock, &version, sizeof(version)); + if (r) + return; + + if (version & 1) + ++version; /* first time write, random junk */ + + ++version; kvm_write_guest(kvm, wall_clock, &version, sizeof(version));