From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Safonov Subject: [PATCHv5 11/37] kernel: Add do_timens_ktime_to_host() helper Date: Mon, 29 Jul 2019 22:56:53 +0100 Message-ID: <20190729215758.28405-12-dima@arista.com> References: <20190729215758.28405-1-dima@arista.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190729215758.28405-1-dima@arista.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: Dmitry Safonov <0x7f454c46@gmail.com>, Andrei Vagin , Dmitry Safonov , Adrian Reber , Andrei Vagin , Andy Lutomirski , Arnd Bergmann , Christian Brauner , Cyrill Gorcunov , "Eric W. Biederman" , "H. Peter Anvin" , Ingo Molnar , Jann Horn , Jeff Dike , Oleg Nesterov , Pavel Emelyanov , Shuah Khan , Thomas Gleixner , Vincenzo Frascino , containers@lists.linux-foundation.org, criu@openvz.org, linux-api List-Id: linux-api@vger.kernel.org From: Andrei Vagin The helper subtracts namespace's clock offset from the given time and checks that the result is in [0, KTIME_MAX]. Signed-off-by: Andrei Vagin Co-developed-by: Dmitry Safonov Signed-off-by: Dmitry Safonov --- include/linux/time_namespace.h | 17 ++++++++++++++ kernel/time_namespace.c | 43 ++++++++++++++++++++++++++++++++++ 2 files changed, 60 insertions(+) diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h index 334c1a1c6607..9ba9664ff0ab 100644 --- a/include/linux/time_namespace.h +++ b/include/linux/time_namespace.h @@ -56,6 +56,18 @@ static inline void timens_add_boottime(struct timespec64 *ts) *ts = timespec64_add(*ts, ns_offsets->boottime); } +ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim, + struct timens_offsets *offsets); +static inline ktime_t timens_ktime_to_host(clockid_t clockid, ktime_t tim) +{ + struct timens_offsets *offsets = current->nsproxy->time_ns->offsets; + + if (!offsets) + return tim; + + return do_timens_ktime_to_host(clockid, tim, offsets); +} + #else static inline struct time_namespace *get_time_ns(struct time_namespace *ns) { @@ -82,6 +94,11 @@ static inline int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *ts static inline void timens_add_monotonic(struct timespec64 *ts) {} static inline void timens_add_boottime(struct timespec64 *ts) {} + +static inline ktime_t timens_ktime_to_host(clockid_t clockid, ktime_t tim) +{ + return tim; +} #endif #endif /* _LINUX_TIMENS_H */ diff --git a/kernel/time_namespace.c b/kernel/time_namespace.c index f849c59f1108..9807c5c90cb2 100644 --- a/kernel/time_namespace.c +++ b/kernel/time_namespace.c @@ -16,6 +16,49 @@ #include #include +ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim, + struct timens_offsets *ns_offsets) +{ + ktime_t offset; + + switch (clockid) { + case CLOCK_MONOTONIC: + offset = timespec64_to_ktime(ns_offsets->monotonic); + break; + case CLOCK_BOOTTIME: + case CLOCK_BOOTTIME_ALARM: + offset = timespec64_to_ktime(ns_offsets->boottime); + break; + default: + return tim; + } + + /* + * Check that @tim value is in [offset, KTIME_MAX + offset] + * and subtract offset. + */ + if (tim < offset) { + /* + * User can specify @tim *absolute* value - if it's lesser than + * the time namespace's offset - it's already expired. + */ + tim = 0; + } else if (KTIME_MAX - tim < -offset) { + /* + * User-supplied @tim may be close or even equal KTIME_MAX + * and time namespace offset can be negative. + * Let's check (tim - offset) for an overflow. + * Return KTIME_MAX in such case, as the time value is + * thousands *years* in future anyway. + */ + tim = KTIME_MAX; + } else { + tim = ktime_sub(tim, offset); + } + + return tim; +} + static struct ucounts *inc_time_namespaces(struct user_namespace *ns) { return inc_ucount(ns, current_euid(), UCOUNT_TIME_NAMESPACES); -- 2.22.0