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- // SPDX-License-Identifier: GPL-2.0
- /*
- * Author: Andrei Vagin <[email protected]>
- * Author: Dmitry Safonov <[email protected]>
- */
- #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_ACCOUNT);
- if (!ns)
- goto fail_dec;
- refcount_set(&ns->ns.count, 1);
- ns->vvar_page = alloc_page(GFP_KERNEL_ACCOUNT | __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 time_namespace *ns)
- {
- 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));
- }
- void timens_commit(struct task_struct *tsk, struct time_namespace *ns)
- {
- timens_set_vvar_page(tsk, ns);
- vdso_join_timens(tsk, ns);
- }
- static int timens_install(struct nsset *nsset, struct ns_common *new)
- {
- struct nsproxy *nsproxy = nsset->nsproxy;
- struct time_namespace *ns = to_time_ns(new);
- if (!current_is_single_threaded())
- return -EUSERS;
- if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
- !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
- return -EPERM;
- 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;
- }
- void 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);
- /* create_new_namespaces() already incremented the ref counter */
- if (nsproxy->time_ns == nsproxy->time_ns_for_children)
- return;
- get_time_ns(ns);
- put_time_ns(nsproxy->time_ns);
- nsproxy->time_ns = ns;
- timens_commit(tsk, ns);
- }
- 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)
- {
- char *clock;
- switch (clockid) {
- case CLOCK_BOOTTIME:
- clock = "boottime";
- break;
- case CLOCK_MONOTONIC:
- clock = "monotonic";
- break;
- default:
- clock = "unknown";
- break;
- }
- seq_printf(m, "%-10s %10lld %9ld\n", clock, 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 = {
- .ns.count = REFCOUNT_INIT(3),
- .user_ns = &init_user_ns,
- .ns.inum = PROC_TIME_INIT_INO,
- .ns.ops = &timens_operations,
- .frozen_offsets = true,
- };
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