From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754325Ab2GaGgP (ORCPT ); Tue, 31 Jul 2012 02:36:15 -0400 Received: from e37.co.us.ibm.com ([32.97.110.158]:43510 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752936Ab2GaGgK (ORCPT ); Tue, 31 Jul 2012 02:36:10 -0400 From: John Stultz To: linux-kernel Cc: John Stultz , Ingo Molnar , Peter Zijlstra , Prarit Bhargava , Thomas Gleixner , Zhouping Liu , CAI Qian Subject: [PATCH 2/2] [RFC] time: Limit time values that would overflow ktime_t Date: Tue, 31 Jul 2012 02:35:48 -0400 Message-Id: <1343716548-38742-3-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1343716548-38742-1-git-send-email-john.stultz@linaro.org> References: <1343716548-38742-1-git-send-email-john.stultz@linaro.org> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12073106-7408-0000-0000-00000739B20D Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We could observe unexpected behavior if the time is set to a value large enough to overflow a 64bit ktime_t (which is something larger then the year 2264). So check timekeeping inputs to make sure we don't set the time to a value that overflows ktime_t. Note: This does not protect from setting the time close to overflowing ktime_t and then letting natural accumulation cause the overflow. Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Prarit Bhargava Cc: Thomas Gleixner Cc: Zhouping Liu Cc: CAI Qian Reported-by: CAI Qian Signed-off-by: John Stultz --- kernel/time/timekeeping.c | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 96179ab..78bccd0 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -92,7 +92,7 @@ __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock); /* flag for if timekeeping is suspended */ int __read_mostly timekeeping_suspended; - +#define TWENTY_YEARS (20LL*365*24*60*60) /** * timekeeper_setup_internals - Set up internals to use clocksource clock. @@ -387,6 +387,9 @@ int do_settimeofday(const struct timespec *tv) if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC) return -EINVAL; + if ((unsigned long long)tv->tv_sec >= KTIME_SEC_MAX) + return -EINVAL; + write_seqlock_irqsave(&timekeeper.lock, flags); timekeeping_forward_now(); @@ -418,6 +421,8 @@ EXPORT_SYMBOL(do_settimeofday); int timekeeping_inject_offset(struct timespec *ts) { unsigned long flags; + struct timespec tmp; + int ret = 0; if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC) return -EINVAL; @@ -426,10 +431,17 @@ int timekeeping_inject_offset(struct timespec *ts) timekeeping_forward_now(); - timekeeper.xtime = timespec_add(timekeeper.xtime, *ts); + /* Make sure the increased value won't cause ktime_t trouble */ + tmp = timespec_add(timekeeper.xtime, *ts); + if ((unsigned long long)tmp.tv_sec >= KTIME_SEC_MAX) { + ret= -EINVAL; + goto error; + } + timekeeper.xtime = tmp; timekeeper.wall_to_monotonic = timespec_sub(timekeeper.wall_to_monotonic, *ts); +error: /* even if we error out, we forwarded the time, so call update */ timekeeping_update(true); write_sequnlock_irqrestore(&timekeeper.lock, flags); @@ -437,7 +449,7 @@ int timekeeping_inject_offset(struct timespec *ts) /* signal hrtimers about time change */ clock_was_set(); - return 0; + return ret; } EXPORT_SYMBOL(timekeeping_inject_offset); @@ -599,6 +611,16 @@ void __init timekeeping_init(void) read_persistent_clock(&now); read_boot_clock(&boot); + /* + * Check to make sure the persistent clock + * didn't return something crazy. + */ + if (now.tv_sec > (KTIME_SEC_MAX - TWENTY_YEARS)) { + printk("WARNING: Persistent clock returned a year greater then" + " 2242. Capping at 2242.\n"); + now.tv_sec = KTIME_SEC_MAX - TWENTY_YEARS; + } + seqlock_init(&timekeeper.lock); ntp_init(); -- 1.7.9.5