From: Dmitry Safonov <dima@arista.com>
To: linux-kernel@vger.kernel.org
Cc: Dmitry Safonov <0x7f454c46@gmail.com>,
Andrei Vagin <avagin@gmail.com>, Dmitry Safonov <dima@arista.com>,
Adrian Reber <adrian@lisas.de>, Andrei Vagin <avagin@openvz.org>,
Andy Lutomirski <luto@kernel.org>,
Christian Brauner <christian.brauner@ubuntu.com>,
Cyrill Gorcunov <gorcunov@openvz.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Jeff Dike <jdike@addtoit.com>, Oleg Nesterov <oleg@redhat.com>,
Pavel Emelyanov <xemul@virtuozzo.com>,
Shuah Khan <shuah@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
containers@lists.linux-foundation.org, criu@openvz.org,
linux-api@vger.kernel.org, x86@kernel.org
Subject: [RFC 10/20] x86/vdso: Use set_normalized_timespec() to avoid 32 bit overflow
Date: Wed, 19 Sep 2018 21:50:27 +0100 [thread overview]
Message-ID: <20180919205037.9574-11-dima@arista.com> (raw)
In-Reply-To: <20180919205037.9574-1-dima@arista.com>
From: Andrei Vagin <avagin@gmail.com>
ts->tv_nsec + offset->tv_nsec
On 32 bit machines that sum can be larger than (1 << 31) and therefor
result in a negative value which screws up the result completely.
Signed-off-by: Andrei Vagin <avagin@openvz.org>
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
arch/x86/entry/vdso/vclock_gettime.c | 35 ++++++++++++++++++++++++++---------
1 file changed, 26 insertions(+), 9 deletions(-)
diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index 0594266740b9..a265e2737a9a 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -231,20 +231,37 @@ notrace static int __always_inline do_realtime(struct timespec *ts)
return mode;
}
+notrace void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
+{
+ while (nsec >= NSEC_PER_SEC) {
+ /*
+ * The following asm() prevents the compiler from
+ * optimising this loop into a modulo operation. See
+ * also __iter_div_u64_rem() in include/linux/time.h
+ */
+ asm("" : "+rm"(nsec));
+ nsec -= NSEC_PER_SEC;
+ ++sec;
+ }
+ while (nsec < 0) {
+ asm("" : "+rm"(nsec));
+ nsec += NSEC_PER_SEC;
+ --sec;
+ }
+ ts->tv_sec = sec;
+ ts->tv_nsec = nsec;
+}
+
notrace static __always_inline void monotonic_to_ns(struct timespec *ts)
{
#ifdef CONFIG_TIME_NS
struct timens_offsets *timens = (struct timens_offsets *) &timens_page;
+ struct timespec offset;
+
+ offset = timespec64_to_timespec(timens->monotonic_time_offset);
+
+ *ts = timespec_add(*ts, offset);
- ts->tv_sec += timens->monotonic_time_offset.tv_sec;
- ts->tv_nsec += timens->monotonic_time_offset.tv_nsec;
- if (ts->tv_nsec > NSEC_PER_SEC) {
- ts->tv_nsec -= NSEC_PER_SEC;
- ts->tv_sec++;
- } else if (ts->tv_nsec < 0) {
- ts->tv_nsec += NSEC_PER_SEC;
- ts->tv_sec--;
- }
#endif
}
--
2.13.6
next prev parent reply other threads:[~2018-09-19 20:52 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-19 20:50 [RFC 00/20] ns: Introduce Time Namespace Dmitry Safonov
2018-09-19 20:50 ` [RFC 01/20] " Dmitry Safonov
2018-09-28 18:20 ` Laurent Vivier
2018-09-19 20:50 ` [RFC 02/20] timens: Add timens_offsets Dmitry Safonov
2018-09-20 18:45 ` Cyrill Gorcunov
2018-09-20 22:14 ` Cyrill Gorcunov
2018-09-19 20:50 ` [RFC 03/20] timens: Introduce CLOCK_MONOTONIC offsets Dmitry Safonov
2018-09-19 20:50 ` [RFC 04/20] timens: Introduce CLOCK_BOOTTIME offset Dmitry Safonov
2018-09-30 3:18 ` [LKP] [timens] 3cc8de9dcb: RIP:posix_get_boottime kernel test robot
2018-09-19 20:50 ` [RFC 05/20] timerfd/timens: Take into account ns clock offsets Dmitry Safonov
2018-09-19 20:50 ` [RFC 06/20] kernel: Take into account timens clock offsets in clock_nanosleep Dmitry Safonov
2018-09-19 20:50 ` [RFC 07/20] timens: Shift /proc/uptime Dmitry Safonov
2018-09-19 20:50 ` [RFC 08/20] x86/vdso: Restrict splitting vvar vma Dmitry Safonov
2018-09-19 20:50 ` [RFC 09/20] x86/vdso/timens: Add offsets page in vvar Dmitry Safonov
2018-09-19 20:50 ` Dmitry Safonov [this message]
2018-09-19 20:50 ` [RFC 11/20] x86/vdso: Purge timens page on setns()/unshare()/clone() Dmitry Safonov
2018-09-19 20:50 ` [RFC 12/20] x86/vdso: Look for vvar vma to purge timens page Dmitry Safonov
2018-09-19 20:50 ` [RFC 13/20] posix-timers/timens: Take into account clock offsets Dmitry Safonov
2018-09-30 3:11 ` [LKP] [posix] 25217c6e39: BUG:KASAN:null-ptr-deref_in_c kernel test robot
2018-09-19 20:50 ` [RFC 14/20] timens: Add align for timens_offsets Dmitry Safonov
2018-09-19 20:50 ` [RFC 15/20] timens: Optimize zero-offsets Dmitry Safonov
2018-09-19 20:50 ` [RFC 16/20] selftest: Add Time Namespace test for supported clocks Dmitry Safonov
2018-09-24 21:36 ` Shuah Khan
2018-09-19 20:50 ` [RFC 17/20] selftest/timens: Add test for timerfd Dmitry Safonov
2018-09-19 20:50 ` [RFC 18/20] selftest/timens: Add test for clock_nanosleep Dmitry Safonov
2018-09-19 20:50 ` [RFC 19/20] timens/selftest: Add procfs selftest Dmitry Safonov
2018-09-19 20:50 ` [RFC 20/20] timens/selftest: Add timer offsets test Dmitry Safonov
2018-09-21 12:27 ` [RFC 00/20] ns: Introduce Time Namespace Eric W. Biederman
2018-09-24 20:51 ` Andrey Vagin
2018-09-24 22:02 ` Eric W. Biederman
2018-09-25 1:42 ` Andrey Vagin
2018-09-26 17:36 ` Eric W. Biederman
2018-09-26 17:59 ` Dmitry Safonov
2018-09-27 21:30 ` Thomas Gleixner
2018-09-27 21:41 ` Thomas Gleixner
2018-10-01 23:20 ` Andrey Vagin
2018-10-02 6:15 ` Thomas Gleixner
2018-10-02 21:05 ` Dmitry Safonov
2018-10-02 21:26 ` Thomas Gleixner
2018-09-28 17:03 ` Eric W. Biederman
2018-09-28 19:32 ` Thomas Gleixner
2018-10-01 9:05 ` Eric W. Biederman
2018-10-01 9:15 ` Setting monotonic time? Eric W. Biederman
2018-10-01 18:52 ` Thomas Gleixner
2018-10-02 20:00 ` Arnd Bergmann
2018-10-02 20:06 ` Thomas Gleixner
2018-10-03 4:50 ` Eric W. Biederman
2018-10-03 5:25 ` Thomas Gleixner
2018-10-03 6:14 ` Eric W. Biederman
2018-10-03 7:02 ` Arnd Bergmann
2018-10-03 6:14 ` Thomas Gleixner
2018-10-01 20:51 ` Andrey Vagin
2018-10-02 6:16 ` Thomas Gleixner
2018-10-21 1:41 ` [RFC 00/20] ns: Introduce Time Namespace Andrei Vagin
2018-10-21 3:54 ` Andrei Vagin
2018-10-29 20:33 ` Thomas Gleixner
2018-10-29 21:21 ` Eric W. Biederman
2018-10-29 21:36 ` Thomas Gleixner
2018-10-31 16:26 ` Andrei Vagin
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