From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02335C433F5 for ; Thu, 9 Dec 2021 12:50:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232130AbhLIMyP (ORCPT ); Thu, 9 Dec 2021 07:54:15 -0500 Received: from szxga01-in.huawei.com ([45.249.212.187]:32894 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230471AbhLIMyO (ORCPT ); Thu, 9 Dec 2021 07:54:14 -0500 Received: from dggpeml500026.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4J8v5Z49TnzcbTM; Thu, 9 Dec 2021 20:50:26 +0800 (CST) Received: from dggpeml500003.china.huawei.com (7.185.36.200) by dggpeml500026.china.huawei.com (7.185.36.106) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Thu, 9 Dec 2021 20:50:39 +0800 Received: from [10.174.177.173] (10.174.177.173) by dggpeml500003.china.huawei.com (7.185.36.200) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Thu, 9 Dec 2021 20:50:39 +0800 Message-ID: <26c3b5d5-c765-1650-568b-d054a92bcba9@huawei.com> Date: Thu, 9 Dec 2021 20:50:38 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [PATCH] time: Normalize timespec64 before timespec64_compare() Content-Language: en-US To: , , CC: , , References: <20211202130707.3910459-1-liaoyu15@huawei.com> From: Yu Liao In-Reply-To: <20211202130707.3910459-1-liaoyu15@huawei.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.173] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpeml500003.china.huawei.com (7.185.36.200) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Is there any comments about this patch? BTW, is it necessary to add set_normalized_timespec64 to timespec64_compare? Thanks, Yu On 2021/12/2 21:07, Yu Liao wrote: > Passing unnormalized timespec64 to timespec64_compare() may cause > incorrect results. > > For example: > wall_to_monotonic = {tv_sec = -10, tv_nsec = 900000000} > ts_delta = {tv_sec = -9, tv_nsec = -900000000} > > timespec64_compare() returns -1, but actually wall_to_monotonic > ts_delta. > This will cause wall_to_monotonic to become a positive number. > > Use timespec64_sub() instead of direct subtraction to avoid this. > > Signed-off-by: Yu Liao > --- > include/linux/time64.h | 2 ++ > kernel/time/timekeeping.c | 3 +-- > 2 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/include/linux/time64.h b/include/linux/time64.h > index 81b9686a2079..f74a36d253cd 100644 > --- a/include/linux/time64.h > +++ b/include/linux/time64.h > @@ -50,6 +50,8 @@ static inline int timespec64_equal(const struct timespec64 *a, > * lhs < rhs: return <0 > * lhs == rhs: return 0 > * lhs > rhs: return >0 > + * > + * Note: Both lhs and rhs must be normalized. > */ > static inline int timespec64_compare(const struct timespec64 *lhs, const struct timespec64 *rhs) > { > diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c > index b348749a9fc6..dcdcb85121e4 100644 > --- a/kernel/time/timekeeping.c > +++ b/kernel/time/timekeeping.c > @@ -1306,8 +1306,7 @@ int do_settimeofday64(const struct timespec64 *ts) > timekeeping_forward_now(tk); > > xt = tk_xtime(tk); > - ts_delta.tv_sec = ts->tv_sec - xt.tv_sec; > - ts_delta.tv_nsec = ts->tv_nsec - xt.tv_nsec; > + ts_delta = timespec64_sub(*ts, xt); > > if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) { > ret = -EINVAL;