From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932068AbaEIQb6 (ORCPT ); Fri, 9 May 2014 12:31:58 -0400 Received: from terminus.zytor.com ([198.137.202.10]:49019 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757082AbaEIQbz (ORCPT ); Fri, 9 May 2014 12:31:55 -0400 Date: Fri, 9 May 2014 09:31:40 -0700 From: tip-bot for Boris Ostrovsky Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, tglx@linutronix.de In-Reply-To: <1399648287-15178-1-git-send-email-boris.ostrovsky@oracle.com> References: <1399648287-15178-1-git-send-email-boris.ostrovsky@oracle.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86, vdso, time: Cast tv_nsec to u64 for proper shifting in update_vsyscall() Git-Commit-ID: 28b92e09e25bdc0ae864b22eacf195a74f861389 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: 28b92e09e25bdc0ae864b22eacf195a74f861389 Gitweb: http://git.kernel.org/tip/28b92e09e25bdc0ae864b22eacf195a74f861389 Author: Boris Ostrovsky AuthorDate: Fri, 9 May 2014 11:11:27 -0400 Committer: H. Peter Anvin CommitDate: Fri, 9 May 2014 08:45:52 -0700 x86, vdso, time: Cast tv_nsec to u64 for proper shifting in update_vsyscall() With tk->wall_to_monotonic.tv_nsec being a 32-bit value on 32-bit systems, (tk->wall_to_monotonic.tv_nsec << tk->shift) in update_vsyscall() may lose upper bits or, worse, add them since compiler will do this: (u64)(tk->wall_to_monotonic.tv_nsec << tk->shift) instead of ((u64)tk->wall_to_monotonic.tv_nsec << tk->shift) So if, for example, tv_nsec is 0x800000 and shift is 8 we will end up with 0xffffffff80000000 instead of 0x80000000. And then we are stuck in the subsequent 'while' loop. We need an explicit cast. Signed-off-by: Boris Ostrovsky Link: http://lkml.kernel.org/r/1399648287-15178-1-git-send-email-boris.ostrovsky@oracle.com Acked-by: Konrad Rzeszutek Wilk Cc: # v3.14 Signed-off-by: H. Peter Anvin --- arch/x86/kernel/vsyscall_gtod.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/vsyscall_gtod.c b/arch/x86/kernel/vsyscall_gtod.c index f9c6e56..9531fbb 100644 --- a/arch/x86/kernel/vsyscall_gtod.c +++ b/arch/x86/kernel/vsyscall_gtod.c @@ -43,7 +43,7 @@ void update_vsyscall(struct timekeeper *tk) vdata->monotonic_time_sec = tk->xtime_sec + tk->wall_to_monotonic.tv_sec; vdata->monotonic_time_snsec = tk->xtime_nsec - + (tk->wall_to_monotonic.tv_nsec + + ((u64)tk->wall_to_monotonic.tv_nsec << tk->shift); while (vdata->monotonic_time_snsec >= (((u64)NSEC_PER_SEC) << tk->shift)) {