1 // SPDX-License-Identifier: GPL-2.0
3 * Author: Andrei Vagin <avagin@openvz.org>
4 * Author: Dmitry Safonov <dima@arista.com>
7 #include <linux/time_namespace.h>
8 #include <linux/user_namespace.h>
9 #include <linux/sched/signal.h>
10 #include <linux/sched/task.h>
11 #include <linux/clocksource.h>
12 #include <linux/seq_file.h>
13 #include <linux/proc_ns.h>
14 #include <linux/export.h>
15 #include <linux/time.h>
16 #include <linux/slab.h>
17 #include <linux/cred.h>
18 #include <linux/err.h>
21 #include <vdso/datapage.h>
23 ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim,
24 struct timens_offsets *ns_offsets)
30 offset = timespec64_to_ktime(ns_offsets->monotonic);
33 case CLOCK_BOOTTIME_ALARM:
34 offset = timespec64_to_ktime(ns_offsets->boottime);
41 * Check that @tim value is in [offset, KTIME_MAX + offset]
42 * and subtract offset.
46 * User can specify @tim *absolute* value - if it's lesser than
47 * the time namespace's offset - it's already expired.
51 tim = ktime_sub(tim, offset);
52 if (unlikely(tim > KTIME_MAX))
59 static struct ucounts *inc_time_namespaces(struct user_namespace *ns)
61 return inc_ucount(ns, current_euid(), UCOUNT_TIME_NAMESPACES);
64 static void dec_time_namespaces(struct ucounts *ucounts)
66 dec_ucount(ucounts, UCOUNT_TIME_NAMESPACES);
70 * clone_time_ns - Clone a time namespace
71 * @user_ns: User namespace which owns a new namespace.
72 * @old_ns: Namespace to clone
74 * Clone @old_ns and set the clone refcount to 1
76 * Return: The new namespace or ERR_PTR.
78 static struct time_namespace *clone_time_ns(struct user_namespace *user_ns,
79 struct time_namespace *old_ns)
81 struct time_namespace *ns;
82 struct ucounts *ucounts;
86 ucounts = inc_time_namespaces(user_ns);
91 ns = kmalloc(sizeof(*ns), GFP_KERNEL);
97 ns->vvar_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
101 err = ns_alloc_inum(&ns->ns);
105 ns->ucounts = ucounts;
106 ns->ns.ops = &timens_operations;
107 ns->user_ns = get_user_ns(user_ns);
108 ns->offsets = old_ns->offsets;
109 ns->frozen_offsets = false;
113 __free_page(ns->vvar_page);
117 dec_time_namespaces(ucounts);
123 * copy_time_ns - Create timens_for_children from @old_ns
124 * @flags: Cloning flags
125 * @user_ns: User namespace which owns a new namespace.
126 * @old_ns: Namespace to clone
128 * If CLONE_NEWTIME specified in @flags, creates a new timens_for_children;
129 * adds a refcounter to @old_ns otherwise.
131 * Return: timens_for_children namespace or ERR_PTR.
133 struct time_namespace *copy_time_ns(unsigned long flags,
134 struct user_namespace *user_ns, struct time_namespace *old_ns)
136 if (!(flags & CLONE_NEWTIME))
137 return get_time_ns(old_ns);
139 return clone_time_ns(user_ns, old_ns);
142 static struct timens_offset offset_from_ts(struct timespec64 off)
144 struct timens_offset ret;
146 ret.sec = off.tv_sec;
147 ret.nsec = off.tv_nsec;
153 * A time namespace VVAR page has the same layout as the VVAR page which
154 * contains the system wide VDSO data.
156 * For a normal task the VVAR pages are installed in the normal ordering:
160 * TIMENS <- Not really required
162 * Now for a timens task the pages are installed in the following order:
168 * The check for vdso_data->clock_mode is in the unlikely path of
169 * the seq begin magic. So for the non-timens case most of the time
170 * 'seq' is even, so the branch is not taken.
172 * If 'seq' is odd, i.e. a concurrent update is in progress, the extra check
173 * for vdso_data->clock_mode is a non-issue. The task is spin waiting for the
174 * update to finish and for 'seq' to become even anyway.
176 * Timens page has vdso_data->clock_mode set to VDSO_CLOCKMODE_TIMENS which
177 * enforces the time namespace handling path.
179 static void timens_setup_vdso_data(struct vdso_data *vdata,
180 struct time_namespace *ns)
182 struct timens_offset *offset = vdata->offset;
183 struct timens_offset monotonic = offset_from_ts(ns->offsets.monotonic);
184 struct timens_offset boottime = offset_from_ts(ns->offsets.boottime);
187 vdata->clock_mode = VDSO_CLOCKMODE_TIMENS;
188 offset[CLOCK_MONOTONIC] = monotonic;
189 offset[CLOCK_MONOTONIC_RAW] = monotonic;
190 offset[CLOCK_MONOTONIC_COARSE] = monotonic;
191 offset[CLOCK_BOOTTIME] = boottime;
192 offset[CLOCK_BOOTTIME_ALARM] = boottime;
196 * Protects possibly multiple offsets writers racing each other
197 * and tasks entering the namespace.
199 static DEFINE_MUTEX(offset_lock);
201 static void timens_set_vvar_page(struct task_struct *task,
202 struct time_namespace *ns)
204 struct vdso_data *vdata;
207 if (ns == &init_time_ns)
210 /* Fast-path, taken by every task in namespace except the first. */
211 if (likely(ns->frozen_offsets))
214 mutex_lock(&offset_lock);
215 /* Nothing to-do: vvar_page has been already initialized. */
216 if (ns->frozen_offsets)
219 ns->frozen_offsets = true;
220 vdata = arch_get_vdso_data(page_address(ns->vvar_page));
222 for (i = 0; i < CS_BASES; i++)
223 timens_setup_vdso_data(&vdata[i], ns);
226 mutex_unlock(&offset_lock);
229 void free_time_ns(struct kref *kref)
231 struct time_namespace *ns;
233 ns = container_of(kref, struct time_namespace, kref);
234 dec_time_namespaces(ns->ucounts);
235 put_user_ns(ns->user_ns);
236 ns_free_inum(&ns->ns);
237 __free_page(ns->vvar_page);
241 static struct time_namespace *to_time_ns(struct ns_common *ns)
243 return container_of(ns, struct time_namespace, ns);
246 static struct ns_common *timens_get(struct task_struct *task)
248 struct time_namespace *ns = NULL;
249 struct nsproxy *nsproxy;
252 nsproxy = task->nsproxy;
254 ns = nsproxy->time_ns;
259 return ns ? &ns->ns : NULL;
262 static struct ns_common *timens_for_children_get(struct task_struct *task)
264 struct time_namespace *ns = NULL;
265 struct nsproxy *nsproxy;
268 nsproxy = task->nsproxy;
270 ns = nsproxy->time_ns_for_children;
275 return ns ? &ns->ns : NULL;
278 static void timens_put(struct ns_common *ns)
280 put_time_ns(to_time_ns(ns));
283 static int timens_install(struct nsproxy *nsproxy, struct ns_common *new)
285 struct time_namespace *ns = to_time_ns(new);
288 if (!current_is_single_threaded())
291 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
292 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
295 timens_set_vvar_page(current, ns);
297 err = vdso_join_timens(current, ns);
302 put_time_ns(nsproxy->time_ns);
303 nsproxy->time_ns = ns;
306 put_time_ns(nsproxy->time_ns_for_children);
307 nsproxy->time_ns_for_children = ns;
311 int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk)
313 struct ns_common *nsc = &nsproxy->time_ns_for_children->ns;
314 struct time_namespace *ns = to_time_ns(nsc);
317 /* create_new_namespaces() already incremented the ref counter */
318 if (nsproxy->time_ns == nsproxy->time_ns_for_children)
321 timens_set_vvar_page(tsk, ns);
323 err = vdso_join_timens(tsk, ns);
328 put_time_ns(nsproxy->time_ns);
329 nsproxy->time_ns = ns;
334 static struct user_namespace *timens_owner(struct ns_common *ns)
336 return to_time_ns(ns)->user_ns;
339 static void show_offset(struct seq_file *m, int clockid, struct timespec64 *ts)
347 case CLOCK_MONOTONIC:
354 seq_printf(m, "%-10s %10lld %9ld\n", clock, ts->tv_sec, ts->tv_nsec);
357 void proc_timens_show_offsets(struct task_struct *p, struct seq_file *m)
359 struct ns_common *ns;
360 struct time_namespace *time_ns;
362 ns = timens_for_children_get(p);
365 time_ns = to_time_ns(ns);
367 show_offset(m, CLOCK_MONOTONIC, &time_ns->offsets.monotonic);
368 show_offset(m, CLOCK_BOOTTIME, &time_ns->offsets.boottime);
369 put_time_ns(time_ns);
372 int proc_timens_set_offset(struct file *file, struct task_struct *p,
373 struct proc_timens_offset *offsets, int noffsets)
375 struct ns_common *ns;
376 struct time_namespace *time_ns;
377 struct timespec64 tp;
380 ns = timens_for_children_get(p);
383 time_ns = to_time_ns(ns);
385 if (!file_ns_capable(file, time_ns->user_ns, CAP_SYS_TIME)) {
386 put_time_ns(time_ns);
390 for (i = 0; i < noffsets; i++) {
391 struct proc_timens_offset *off = &offsets[i];
393 switch (off->clockid) {
394 case CLOCK_MONOTONIC:
398 ktime_get_boottime_ts64(&tp);
407 if (off->val.tv_sec > KTIME_SEC_MAX ||
408 off->val.tv_sec < -KTIME_SEC_MAX)
411 tp = timespec64_add(tp, off->val);
413 * KTIME_SEC_MAX is divided by 2 to be sure that KTIME_MAX is
416 if (tp.tv_sec < 0 || tp.tv_sec > KTIME_SEC_MAX / 2)
420 mutex_lock(&offset_lock);
421 if (time_ns->frozen_offsets) {
427 /* Don't report errors after this line */
428 for (i = 0; i < noffsets; i++) {
429 struct proc_timens_offset *off = &offsets[i];
430 struct timespec64 *offset = NULL;
432 switch (off->clockid) {
433 case CLOCK_MONOTONIC:
434 offset = &time_ns->offsets.monotonic;
437 offset = &time_ns->offsets.boottime;
445 mutex_unlock(&offset_lock);
447 put_time_ns(time_ns);
452 const struct proc_ns_operations timens_operations = {
454 .type = CLONE_NEWTIME,
457 .install = timens_install,
458 .owner = timens_owner,
461 const struct proc_ns_operations timens_for_children_operations = {
462 .name = "time_for_children",
463 .real_ns_name = "time",
464 .type = CLONE_NEWTIME,
465 .get = timens_for_children_get,
467 .install = timens_install,
468 .owner = timens_owner,
471 struct time_namespace init_time_ns = {
472 .kref = KREF_INIT(3),
473 .user_ns = &init_user_ns,
474 .ns.inum = PROC_TIME_INIT_INO,
475 .ns.ops = &timens_operations,
476 .frozen_offsets = true,
479 static int __init time_ns_init(void)
483 subsys_initcall(time_ns_init);