// 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;
}
struct page *find_timens_vvar_page(struct vm_area_struct *vma)
{
if (likely(vma->vm_mm == current->mm))
return current->nsproxy->time_ns->vvar_page;
/*
* VM_PFNMAP | VM_IO protect .fault() handler from being called
* through interfaces like /proc/$pid/mem or
* process_vm_{readv,writev}() as long as there's no .access()
* in special_mapping_vmops().
* For more details check_vma_flags() and __access_remote_vm()
*/
WARN(1, "vvar_page accessed remotely");
return NULL;
}
/*
* 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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