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linux
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// SPDX-License-Identifier: GPL-2.0 /* * Author: Andrei Vagin <avagin@openvz.org> * Author: Dmitry Safonov <dima@arista.com> */ #include <linux/time_namespace.h> #include <linux/user_namespace.h> #include <linux/sched/signal.h> #include <linux/sched/task.h> #include <linux/clocksource.h> #include <linux/seq_file.h> #include <linux/proc_ns.h> #include <linux/export.h> #include <linux/time.h> #include <linux/slab.h> #include <linux/cred.h> #include <linux/err.h> #include <linux/mm.h> #include <vdso/datapage.h> 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 { tim = ktime_sub(tim, offset); if (unlikely(tim > KTIME_MAX)) tim = KTIME_MAX; } return tim; } static struct ucounts *inc_time_namespaces(struct user_namespace *ns) { return inc_ucount(ns, current_euid(), UCOUNT_TIME_NAMESPACES); } static void dec_time_namespaces(struct ucounts *ucounts) { dec_ucount(ucounts, UCOUNT_TIME_NAMESPACES); } /** * clone_time_ns - Clone a time namespace * @user_ns: User namespace which owns a new namespace. * @old_ns: Namespace to clone * * Clone @old_ns and set the clone refcount to 1 * * Return: The new namespace or ERR_PTR. */ static struct time_namespace *clone_time_ns(struct user_namespace *user_ns, struct time_namespace *old_ns) { struct time_namespace *ns; struct ucounts *ucounts; int err; err = -ENOSPC; ucounts = inc_time_namespaces(user_ns); if (!ucounts) goto fail; err = -ENOMEM; ns = kmalloc(sizeof(*ns), GFP_KERNEL); if (!ns) goto fail_dec; kref_init(&ns->kref); ns->vvar_page = alloc_page(GFP_KERNEL | __GFP_ZERO); if (!ns->vvar_page) goto fail_free; err = ns_alloc_inum(&ns->ns); if (err) goto fail_free_page; ns->ucounts = ucounts; ns->ns.ops = &timens_operations; ns->user_ns = get_user_ns(user_ns); ns->offsets = old_ns->offsets; ns->frozen_offsets = false; return ns; fail_free_page: __free_page(ns->vvar_page); fail_free: kfree(ns); fail_dec: dec_time_namespaces(ucounts); fail: return ERR_PTR(err); } /** * copy_time_ns - Create timens_for_children from @old_ns * @flags: Cloning flags * @user_ns: User namespace which owns a new namespace. * @old_ns: Namespace to clone * * If CLONE_NEWTIME specified in @flags, creates a new timens_for_children; * adds a refcounter to @old_ns otherwise. * * Return: timens_for_children namespace or ERR_PTR. */ struct time_namespace *copy_time_ns(unsigned long flags, struct user_namespace *user_ns, struct time_namespace *old_ns) { if (!(flags & CLONE_NEWTIME)) return get_time_ns(old_ns); return clone_time_ns(user_ns, old_ns); } static struct timens_offset offset_from_ts(struct timespec64 off) { struct timens_offset ret; ret.sec = off.tv_sec; ret.nsec = off.tv_nsec; return ret; } /* * A time namespace VVAR page has the same layout as the VVAR page which * contains the system wide VDSO data. * * For a normal task the VVAR pages are installed in the normal ordering: * VVAR * PVCLOCK * HVCLOCK * TIMENS <- Not really required * * Now for a timens task the pages are installed in the following order: * TIMENS * PVCLOCK * HVCLOCK * VVAR * * The check for vdso_data->clock_mode is in the unlikely path of * the seq begin magic. So for the non-timens case most of the time * 'seq' is even, so the branch is not taken. * * If 'seq' is odd, i.e. a concurrent update is in progress, the extra check * for vdso_data->clock_mode is a non-issue. The task is spin waiting for the * update to finish and for 'seq' to become even anyway. * * Timens page has vdso_data->clock_mode set to VDSO_CLOCKMODE_TIMENS which * enforces the time namespace handling path. */ static void timens_setup_vdso_data(struct vdso_data *vdata, struct time_namespace *ns) { struct timens_offset *offset = vdata->offset; struct timens_offset monotonic = offset_from_ts(ns->offsets.monotonic); struct timens_offset boottime = offset_from_ts(ns->offsets.boottime); vdata->seq = 1; vdata->clock_mode = VDSO_CLOCKMODE_TIMENS; offset[CLOCK_MONOTONIC] = monotonic; offset[CLOCK_MONOTONIC_RAW] = monotonic; offset[CLOCK_MONOTONIC_COARSE] = monotonic; offset[CLOCK_BOOTTIME] = boottime; offset[CLOCK_BOOTTIME_ALARM] = boottime; } /* * Protects possibly multiple offsets writers racing each other * and tasks entering the namespace. */ static DEFINE_MUTEX(offset_lock); static void timens_set_vvar_page(struct task_struct *task, struct time_namespace *ns) { struct vdso_data *vdata; unsigned int i; if (ns == &init_time_ns) return; /* Fast-path, taken by every task in namespace except the first. */ if (likely(ns->frozen_offsets)) return; mutex_lock(&offset_lock); /* Nothing to-do: vvar_page has been already initialized. */ if (ns->frozen_offsets) goto out; ns->frozen_offsets = true; vdata = arch_get_vdso_data(page_address(ns->vvar_page)); for (i = 0; i < CS_BASES; i++) timens_setup_vdso_data(&vdata[i], ns); out: mutex_unlock(&offset_lock); } void free_time_ns(struct kref *kref) { struct time_namespace *ns; ns = container_of(kref, struct time_namespace, kref); dec_time_namespaces(ns->ucounts); put_user_ns(ns->user_ns); ns_free_inum(&ns->ns); __free_page(ns->vvar_page); kfree(ns); } static struct time_namespace *to_time_ns(struct ns_common *ns) { return container_of(ns, struct time_namespace, ns); } static struct ns_common *timens_get(struct task_struct *task) { struct time_namespace *ns = NULL; struct nsproxy *nsproxy; task_lock(task); nsproxy = task->nsproxy; if (nsproxy) { ns = nsproxy->time_ns; get_time_ns(ns); } task_unlock(task); return ns ? &ns->ns : NULL; } static struct ns_common *timens_for_children_get(struct task_struct *task) { struct time_namespace *ns = NULL; struct nsproxy *nsproxy; task_lock(task); nsproxy = task->nsproxy; if (nsproxy) { ns = nsproxy->time_ns_for_children; get_time_ns(ns); } task_unlock(task); return ns ? &ns->ns : NULL; } static void timens_put(struct ns_common *ns) { put_time_ns(to_time_ns(ns)); } static int timens_install(struct nsproxy *nsproxy, struct ns_common *new) { struct time_namespace *ns = to_time_ns(new); int err; if (!current_is_single_threaded()) return -EUSERS; if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) return -EPERM; timens_set_vvar_page(current, ns); err = vdso_join_timens(current, ns); if (err) return err; get_time_ns(ns); put_time_ns(nsproxy->time_ns); nsproxy->time_ns = ns; get_time_ns(ns); put_time_ns(nsproxy->time_ns_for_children); nsproxy->time_ns_for_children = ns; return 0; } int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk) { struct ns_common *nsc = &nsproxy->time_ns_for_children->ns; struct time_namespace *ns = to_time_ns(nsc); int err; /* create_new_namespaces() already incremented the ref counter */ if (nsproxy->time_ns == nsproxy->time_ns_for_children) return 0; timens_set_vvar_page(tsk, ns); err = vdso_join_timens(tsk, ns); if (err) return err; get_time_ns(ns); put_time_ns(nsproxy->time_ns); nsproxy->time_ns = ns; return 0; } static struct user_namespace *timens_owner(struct ns_common *ns) { return to_time_ns(ns)->user_ns; } static void show_offset(struct seq_file *m, int clockid, struct timespec64 *ts) { seq_printf(m, "%d %lld %ld\n", clockid, ts->tv_sec, ts->tv_nsec); } void proc_timens_show_offsets(struct task_struct *p, struct seq_file *m) { struct ns_common *ns; struct time_namespace *time_ns; ns = timens_for_children_get(p); if (!ns) return; time_ns = to_time_ns(ns); show_offset(m, CLOCK_MONOTONIC, &time_ns->offsets.monotonic); show_offset(m, CLOCK_BOOTTIME, &time_ns->offsets.boottime); put_time_ns(time_ns); } int proc_timens_set_offset(struct file *file, struct task_struct *p, struct proc_timens_offset *offsets, int noffsets) { struct ns_common *ns; struct time_namespace *time_ns; struct timespec64 tp; int i, err; ns = timens_for_children_get(p); if (!ns) return -ESRCH; time_ns = to_time_ns(ns); if (!file_ns_capable(file, time_ns->user_ns, CAP_SYS_TIME)) { put_time_ns(time_ns); return -EPERM; } for (i = 0; i < noffsets; i++) { struct proc_timens_offset *off = &offsets[i]; switch (off->clockid) { case CLOCK_MONOTONIC: ktime_get_ts64(&tp); break; case CLOCK_BOOTTIME: ktime_get_boottime_ts64(&tp); break; default: err = -EINVAL; goto out; } err = -ERANGE; if (off->val.tv_sec > KTIME_SEC_MAX || off->val.tv_sec < -KTIME_SEC_MAX) goto out; tp = timespec64_add(tp, off->val); /* * KTIME_SEC_MAX is divided by 2 to be sure that KTIME_MAX is * still unreachable. */ if (tp.tv_sec < 0 || tp.tv_sec > KTIME_SEC_MAX / 2) goto out; } mutex_lock(&offset_lock); if (time_ns->frozen_offsets) { err = -EACCES; goto out_unlock; } err = 0; /* Don't report errors after this line */ for (i = 0; i < noffsets; i++) { struct proc_timens_offset *off = &offsets[i]; struct timespec64 *offset = NULL; switch (off->clockid) { case CLOCK_MONOTONIC: offset = &time_ns->offsets.monotonic; break; case CLOCK_BOOTTIME: offset = &time_ns->offsets.boottime; break; } *offset = off->val; } out_unlock: mutex_unlock(&offset_lock); out: put_time_ns(time_ns); return err; } const struct proc_ns_operations timens_operations = { .name = "time", .type = CLONE_NEWTIME, .get = timens_get, .put = timens_put, .install = timens_install, .owner = timens_owner, }; const struct proc_ns_operations timens_for_children_operations = { .name = "time_for_children", .real_ns_name = "time", .type = CLONE_NEWTIME, .get = timens_for_children_get, .put = timens_put, .install = timens_install, .owner = timens_owner, }; struct time_namespace init_time_ns = { .kref = KREF_INIT(3), .user_ns = &init_user_ns, .ns.inum = PROC_TIME_INIT_INO, .ns.ops = &timens_operations, .frozen_offsets = true, }; static int __init time_ns_init(void) { return 0; } subsys_initcall(time_ns_init);
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