Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756384Ab3EJOWY (ORCPT ); Fri, 10 May 2013 10:22:24 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:57344 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755549Ab3EJOWM (ORCPT ); Fri, 10 May 2013 10:22:12 -0400 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, "John Stultz" , "David Engraf" Date: Fri, 10 May 2013 14:39:41 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [022/118] hrtimer: Fix ktime_add_ns() overflow on 32bit architectures In-Reply-To: X-SA-Exim-Connect-IP: 2001:470:1f08:1539:d51a:8785:aa0a:cebe 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 Content-Length: 1988 Lines: 58 3.2.45-rc1 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: Ben Hutchings --- kernel/hrtimer.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -298,6 +298,10 @@ ktime_t ktime_sub_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); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/