From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757211Ab3EFU6c (ORCPT ); Mon, 6 May 2013 16:58:32 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:59244 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756525Ab3EFUqp (ORCPT ); Mon, 6 May 2013 16:46:45 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Engraf , John Stultz Subject: [ 069/115] hrtimer: Fix ktime_add_ns() overflow on 32bit architectures Date: Mon, 6 May 2013 13:45:05 -0700 Message-Id: <20130506203102.622003727@linuxfoundation.org> X-Mailer: git-send-email 1.8.3.rc0.20.gb99dd2e In-Reply-To: <20130506203055.537199268@linuxfoundation.org> References: <20130506203055.537199268@linuxfoundation.org> User-Agent: quilt/0.60-5.1.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Engraf commit 51fd36f3fad8447c487137ae26b9d0b3ce77bb25 upstream. One can trigger an overflow when using ktime_add_ns() on a 32bit architecture not supporting CONFIG_KTIME_SCALAR. When passing a very high value for u64 nsec, e.g. 7881299347898368000 the do_div() function converts this value to seconds (7881299347) which is still to high to pass to the ktime_set() function as long. The result in is a negative value. The problem on my system occurs in the tick-sched.c, tick_nohz_stop_sched_tick() when time_delta is set to timekeeping_max_deferment(). The check for time_delta < KTIME_MAX is valid, thus ktime_add_ns() is called with a too large value resulting in a negative expire value. This leads to an endless loop in the ticker code: time_delta: 7881299347898368000 expires = ktime_add_ns(last_update, time_delta) expires: negative value This fix caps the value to KTIME_MAX. This error doesn't occurs on 64bit or architectures supporting CONFIG_KTIME_SCALAR (e.g. ARM, x86-32). Signed-off-by: David Engraf [jstultz: Minor tweaks to commit message & header] Signed-off-by: John Stultz Signed-off-by: Greg Kroah-Hartman --- kernel/hrtimer.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -276,6 +276,10 @@ ktime_t ktime_add_ns(const ktime_t kt, u } else { unsigned long rem = do_div(nsec, NSEC_PER_SEC); + /* Make sure nsec fits into long */ + if (unlikely(nsec > KTIME_SEC_MAX)) + return (ktime_t){ .tv64 = KTIME_MAX }; + tmp = ktime_set((long)nsec, rem); }