From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754557AbbFWKte (ORCPT ); Tue, 23 Jun 2015 06:49:34 -0400 Received: from mail-pd0-f182.google.com ([209.85.192.182]:35582 "EHLO mail-pd0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753540AbbFWKt1 (ORCPT ); Tue, 23 Jun 2015 06:49:27 -0400 Date: Tue, 23 Jun 2015 18:38:54 +0800 From: Wang YanQing To: john.stultz@linaro.org Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: [PATCH v3] timekeeping: always make sure wall_to_monotonic isn't positive Message-ID: <20150623103854.GA5748@udknight.ahead-top.com> Mail-Followup-To: Wang YanQing , john.stultz@linaro.org, tglx@linutronix.de, linux-kernel@vger.kernel.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.22 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I meet two issues on an IMX6 development board without enable RTC device(so timekeeping_init will initialize the boot time and monotonic to 0). Issue 1:exportfs -a generate: "exportfs: /opt/nfs/arm does not support NFS export" Issue 2:cat /proc/stat: "btime 4294967236" Exact reproduction of the same issues on x86 after run below code: " int main(void) { struct timeval val; int ret; val.tv_sec = 0; val.tv_usec = 0; ret = settimeofday(&val, NULL); return 0; } " Two issues are different symptoms of same problem: The reason is positive wall_to_monotonic push boot time back to the time before Epoch, getboottime will return negative value. In symptom 1: negative boot time cause get_expiry overflow time_t when input expire time is 2147483647, then cache_flush always clear entries just added in ip_map_parse. In symptom 2: show_stat use "unsigned long" to print negative value return by getboottime. This patch fix the problem. Impact: You can't set the CLOCK_REALTIME time prior to (1970 + system uptime). Signed-off-by: Wang YanQing --- Changes v1-v2: 1: fix subject, use "isn't positive" instead of "is negative". 2: rewrite changelog. 3: simplify code as suggested by John Stultz. v2-v3: 1: reword changelog, no change of source code. kernel/time/timekeeping.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index bca3667..4cdb771 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -911,6 +911,7 @@ int do_settimeofday64(const struct timespec64 *ts) struct timekeeper *tk = &tk_core.timekeeper; struct timespec64 ts_delta, xt; unsigned long flags; + int ret = 0; if (!timespec64_valid_strict(ts)) return -EINVAL; @@ -924,10 +925,15 @@ int do_settimeofday64(const struct timespec64 *ts) ts_delta.tv_sec = ts->tv_sec - xt.tv_sec; ts_delta.tv_nsec = ts->tv_nsec - xt.tv_nsec; + if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) { + ret = -EINVAL; + goto out; + } + tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta)); tk_set_xtime(tk, ts); - +out: timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET); write_seqcount_end(&tk_core.seq); @@ -936,7 +942,7 @@ int do_settimeofday64(const struct timespec64 *ts) /* signal hrtimers about time change */ clock_was_set(); - return 0; + return ret; } EXPORT_SYMBOL(do_settimeofday64); @@ -965,7 +971,8 @@ int timekeeping_inject_offset(struct timespec *ts) /* Make sure the proposed value is valid */ tmp = timespec64_add(tk_xtime(tk), ts64); - if (!timespec64_valid_strict(&tmp)) { + if (timespec64_compare(&tk->wall_to_monotonic, &ts64) > 0 || + !timespec64_valid_strict(&tmp)) { ret = -EINVAL; goto error; } -- 1.8.5.6.2.g3d8a54e.dirty