cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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namespace.c (10696B)


      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * Author: Andrei Vagin <avagin@openvz.org>
      4 * Author: Dmitry Safonov <dima@arista.com>
      5 */
      6
      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>
     19#include <linux/mm.h>
     20
     21#include <vdso/datapage.h>
     22
     23ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim,
     24				struct timens_offsets *ns_offsets)
     25{
     26	ktime_t offset;
     27
     28	switch (clockid) {
     29	case CLOCK_MONOTONIC:
     30		offset = timespec64_to_ktime(ns_offsets->monotonic);
     31		break;
     32	case CLOCK_BOOTTIME:
     33	case CLOCK_BOOTTIME_ALARM:
     34		offset = timespec64_to_ktime(ns_offsets->boottime);
     35		break;
     36	default:
     37		return tim;
     38	}
     39
     40	/*
     41	 * Check that @tim value is in [offset, KTIME_MAX + offset]
     42	 * and subtract offset.
     43	 */
     44	if (tim < offset) {
     45		/*
     46		 * User can specify @tim *absolute* value - if it's lesser than
     47		 * the time namespace's offset - it's already expired.
     48		 */
     49		tim = 0;
     50	} else {
     51		tim = ktime_sub(tim, offset);
     52		if (unlikely(tim > KTIME_MAX))
     53			tim = KTIME_MAX;
     54	}
     55
     56	return tim;
     57}
     58
     59static struct ucounts *inc_time_namespaces(struct user_namespace *ns)
     60{
     61	return inc_ucount(ns, current_euid(), UCOUNT_TIME_NAMESPACES);
     62}
     63
     64static void dec_time_namespaces(struct ucounts *ucounts)
     65{
     66	dec_ucount(ucounts, UCOUNT_TIME_NAMESPACES);
     67}
     68
     69/**
     70 * clone_time_ns - Clone a time namespace
     71 * @user_ns:	User namespace which owns a new namespace.
     72 * @old_ns:	Namespace to clone
     73 *
     74 * Clone @old_ns and set the clone refcount to 1
     75 *
     76 * Return: The new namespace or ERR_PTR.
     77 */
     78static struct time_namespace *clone_time_ns(struct user_namespace *user_ns,
     79					  struct time_namespace *old_ns)
     80{
     81	struct time_namespace *ns;
     82	struct ucounts *ucounts;
     83	int err;
     84
     85	err = -ENOSPC;
     86	ucounts = inc_time_namespaces(user_ns);
     87	if (!ucounts)
     88		goto fail;
     89
     90	err = -ENOMEM;
     91	ns = kmalloc(sizeof(*ns), GFP_KERNEL_ACCOUNT);
     92	if (!ns)
     93		goto fail_dec;
     94
     95	refcount_set(&ns->ns.count, 1);
     96
     97	ns->vvar_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
     98	if (!ns->vvar_page)
     99		goto fail_free;
    100
    101	err = ns_alloc_inum(&ns->ns);
    102	if (err)
    103		goto fail_free_page;
    104
    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;
    110	return ns;
    111
    112fail_free_page:
    113	__free_page(ns->vvar_page);
    114fail_free:
    115	kfree(ns);
    116fail_dec:
    117	dec_time_namespaces(ucounts);
    118fail:
    119	return ERR_PTR(err);
    120}
    121
    122/**
    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
    127 *
    128 * If CLONE_NEWTIME specified in @flags, creates a new timens_for_children;
    129 * adds a refcounter to @old_ns otherwise.
    130 *
    131 * Return: timens_for_children namespace or ERR_PTR.
    132 */
    133struct time_namespace *copy_time_ns(unsigned long flags,
    134	struct user_namespace *user_ns, struct time_namespace *old_ns)
    135{
    136	if (!(flags & CLONE_NEWTIME))
    137		return get_time_ns(old_ns);
    138
    139	return clone_time_ns(user_ns, old_ns);
    140}
    141
    142static struct timens_offset offset_from_ts(struct timespec64 off)
    143{
    144	struct timens_offset ret;
    145
    146	ret.sec = off.tv_sec;
    147	ret.nsec = off.tv_nsec;
    148
    149	return ret;
    150}
    151
    152/*
    153 * A time namespace VVAR page has the same layout as the VVAR page which
    154 * contains the system wide VDSO data.
    155 *
    156 * For a normal task the VVAR pages are installed in the normal ordering:
    157 *     VVAR
    158 *     PVCLOCK
    159 *     HVCLOCK
    160 *     TIMENS   <- Not really required
    161 *
    162 * Now for a timens task the pages are installed in the following order:
    163 *     TIMENS
    164 *     PVCLOCK
    165 *     HVCLOCK
    166 *     VVAR
    167 *
    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.
    171 *
    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.
    175 *
    176 * Timens page has vdso_data->clock_mode set to VDSO_CLOCKMODE_TIMENS which
    177 * enforces the time namespace handling path.
    178 */
    179static void timens_setup_vdso_data(struct vdso_data *vdata,
    180				   struct time_namespace *ns)
    181{
    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);
    185
    186	vdata->seq			= 1;
    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;
    193}
    194
    195/*
    196 * Protects possibly multiple offsets writers racing each other
    197 * and tasks entering the namespace.
    198 */
    199static DEFINE_MUTEX(offset_lock);
    200
    201static void timens_set_vvar_page(struct task_struct *task,
    202				struct time_namespace *ns)
    203{
    204	struct vdso_data *vdata;
    205	unsigned int i;
    206
    207	if (ns == &init_time_ns)
    208		return;
    209
    210	/* Fast-path, taken by every task in namespace except the first. */
    211	if (likely(ns->frozen_offsets))
    212		return;
    213
    214	mutex_lock(&offset_lock);
    215	/* Nothing to-do: vvar_page has been already initialized. */
    216	if (ns->frozen_offsets)
    217		goto out;
    218
    219	ns->frozen_offsets = true;
    220	vdata = arch_get_vdso_data(page_address(ns->vvar_page));
    221
    222	for (i = 0; i < CS_BASES; i++)
    223		timens_setup_vdso_data(&vdata[i], ns);
    224
    225out:
    226	mutex_unlock(&offset_lock);
    227}
    228
    229void free_time_ns(struct time_namespace *ns)
    230{
    231	dec_time_namespaces(ns->ucounts);
    232	put_user_ns(ns->user_ns);
    233	ns_free_inum(&ns->ns);
    234	__free_page(ns->vvar_page);
    235	kfree(ns);
    236}
    237
    238static struct time_namespace *to_time_ns(struct ns_common *ns)
    239{
    240	return container_of(ns, struct time_namespace, ns);
    241}
    242
    243static struct ns_common *timens_get(struct task_struct *task)
    244{
    245	struct time_namespace *ns = NULL;
    246	struct nsproxy *nsproxy;
    247
    248	task_lock(task);
    249	nsproxy = task->nsproxy;
    250	if (nsproxy) {
    251		ns = nsproxy->time_ns;
    252		get_time_ns(ns);
    253	}
    254	task_unlock(task);
    255
    256	return ns ? &ns->ns : NULL;
    257}
    258
    259static struct ns_common *timens_for_children_get(struct task_struct *task)
    260{
    261	struct time_namespace *ns = NULL;
    262	struct nsproxy *nsproxy;
    263
    264	task_lock(task);
    265	nsproxy = task->nsproxy;
    266	if (nsproxy) {
    267		ns = nsproxy->time_ns_for_children;
    268		get_time_ns(ns);
    269	}
    270	task_unlock(task);
    271
    272	return ns ? &ns->ns : NULL;
    273}
    274
    275static void timens_put(struct ns_common *ns)
    276{
    277	put_time_ns(to_time_ns(ns));
    278}
    279
    280void timens_commit(struct task_struct *tsk, struct time_namespace *ns)
    281{
    282	timens_set_vvar_page(tsk, ns);
    283	vdso_join_timens(tsk, ns);
    284}
    285
    286static int timens_install(struct nsset *nsset, struct ns_common *new)
    287{
    288	struct nsproxy *nsproxy = nsset->nsproxy;
    289	struct time_namespace *ns = to_time_ns(new);
    290
    291	if (!current_is_single_threaded())
    292		return -EUSERS;
    293
    294	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
    295	    !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
    296		return -EPERM;
    297
    298	get_time_ns(ns);
    299	put_time_ns(nsproxy->time_ns);
    300	nsproxy->time_ns = ns;
    301
    302	get_time_ns(ns);
    303	put_time_ns(nsproxy->time_ns_for_children);
    304	nsproxy->time_ns_for_children = ns;
    305	return 0;
    306}
    307
    308void timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk)
    309{
    310	struct ns_common *nsc = &nsproxy->time_ns_for_children->ns;
    311	struct time_namespace *ns = to_time_ns(nsc);
    312
    313	/* create_new_namespaces() already incremented the ref counter */
    314	if (nsproxy->time_ns == nsproxy->time_ns_for_children)
    315		return;
    316
    317	get_time_ns(ns);
    318	put_time_ns(nsproxy->time_ns);
    319	nsproxy->time_ns = ns;
    320
    321	timens_commit(tsk, ns);
    322}
    323
    324static struct user_namespace *timens_owner(struct ns_common *ns)
    325{
    326	return to_time_ns(ns)->user_ns;
    327}
    328
    329static void show_offset(struct seq_file *m, int clockid, struct timespec64 *ts)
    330{
    331	char *clock;
    332
    333	switch (clockid) {
    334	case CLOCK_BOOTTIME:
    335		clock = "boottime";
    336		break;
    337	case CLOCK_MONOTONIC:
    338		clock = "monotonic";
    339		break;
    340	default:
    341		clock = "unknown";
    342		break;
    343	}
    344	seq_printf(m, "%-10s %10lld %9ld\n", clock, ts->tv_sec, ts->tv_nsec);
    345}
    346
    347void proc_timens_show_offsets(struct task_struct *p, struct seq_file *m)
    348{
    349	struct ns_common *ns;
    350	struct time_namespace *time_ns;
    351
    352	ns = timens_for_children_get(p);
    353	if (!ns)
    354		return;
    355	time_ns = to_time_ns(ns);
    356
    357	show_offset(m, CLOCK_MONOTONIC, &time_ns->offsets.monotonic);
    358	show_offset(m, CLOCK_BOOTTIME, &time_ns->offsets.boottime);
    359	put_time_ns(time_ns);
    360}
    361
    362int proc_timens_set_offset(struct file *file, struct task_struct *p,
    363			   struct proc_timens_offset *offsets, int noffsets)
    364{
    365	struct ns_common *ns;
    366	struct time_namespace *time_ns;
    367	struct timespec64 tp;
    368	int i, err;
    369
    370	ns = timens_for_children_get(p);
    371	if (!ns)
    372		return -ESRCH;
    373	time_ns = to_time_ns(ns);
    374
    375	if (!file_ns_capable(file, time_ns->user_ns, CAP_SYS_TIME)) {
    376		put_time_ns(time_ns);
    377		return -EPERM;
    378	}
    379
    380	for (i = 0; i < noffsets; i++) {
    381		struct proc_timens_offset *off = &offsets[i];
    382
    383		switch (off->clockid) {
    384		case CLOCK_MONOTONIC:
    385			ktime_get_ts64(&tp);
    386			break;
    387		case CLOCK_BOOTTIME:
    388			ktime_get_boottime_ts64(&tp);
    389			break;
    390		default:
    391			err = -EINVAL;
    392			goto out;
    393		}
    394
    395		err = -ERANGE;
    396
    397		if (off->val.tv_sec > KTIME_SEC_MAX ||
    398		    off->val.tv_sec < -KTIME_SEC_MAX)
    399			goto out;
    400
    401		tp = timespec64_add(tp, off->val);
    402		/*
    403		 * KTIME_SEC_MAX is divided by 2 to be sure that KTIME_MAX is
    404		 * still unreachable.
    405		 */
    406		if (tp.tv_sec < 0 || tp.tv_sec > KTIME_SEC_MAX / 2)
    407			goto out;
    408	}
    409
    410	mutex_lock(&offset_lock);
    411	if (time_ns->frozen_offsets) {
    412		err = -EACCES;
    413		goto out_unlock;
    414	}
    415
    416	err = 0;
    417	/* Don't report errors after this line */
    418	for (i = 0; i < noffsets; i++) {
    419		struct proc_timens_offset *off = &offsets[i];
    420		struct timespec64 *offset = NULL;
    421
    422		switch (off->clockid) {
    423		case CLOCK_MONOTONIC:
    424			offset = &time_ns->offsets.monotonic;
    425			break;
    426		case CLOCK_BOOTTIME:
    427			offset = &time_ns->offsets.boottime;
    428			break;
    429		}
    430
    431		*offset = off->val;
    432	}
    433
    434out_unlock:
    435	mutex_unlock(&offset_lock);
    436out:
    437	put_time_ns(time_ns);
    438
    439	return err;
    440}
    441
    442const struct proc_ns_operations timens_operations = {
    443	.name		= "time",
    444	.type		= CLONE_NEWTIME,
    445	.get		= timens_get,
    446	.put		= timens_put,
    447	.install	= timens_install,
    448	.owner		= timens_owner,
    449};
    450
    451const struct proc_ns_operations timens_for_children_operations = {
    452	.name		= "time_for_children",
    453	.real_ns_name	= "time",
    454	.type		= CLONE_NEWTIME,
    455	.get		= timens_for_children_get,
    456	.put		= timens_put,
    457	.install	= timens_install,
    458	.owner		= timens_owner,
    459};
    460
    461struct time_namespace init_time_ns = {
    462	.ns.count	= REFCOUNT_INIT(3),
    463	.user_ns	= &init_user_ns,
    464	.ns.inum	= PROC_TIME_INIT_INO,
    465	.ns.ops		= &timens_operations,
    466	.frozen_offsets	= true,
    467};