Release 4.15 kernel/user_namespace.c

/*
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License as
 *  published by the Free Software Foundation, version 2 of the
 *  License.
 */

#include <linux/export.h>
#include <linux/nsproxy.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/user_namespace.h>
#include <linux/proc_ns.h>
#include <linux/highuid.h>
#include <linux/cred.h>
#include <linux/securebits.h>
#include <linux/keyctl.h>
#include <linux/key-type.h>
#include <keys/user-type.h>
#include <linux/seq_file.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/ctype.h>
#include <linux/projid.h>
#include <linux/fs_struct.h>
#include <linux/bsearch.h>
#include <linux/sort.h>


static struct kmem_cache *user_ns_cachep __read_mostly;
static DEFINE_MUTEX(userns_state_mutex);

static bool new_idmap_permitted(const struct file *file,
				struct user_namespace *ns, int cap_setid,
				struct uid_gid_map *map);
static void free_user_ns(struct work_struct *work);



static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
{
	return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES);
}

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static void dec_user_namespaces(struct ucounts *ucounts)
{
	return dec_ucount(ucounts, UCOUNT_USER_NAMESPACES);
}

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static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
{
	/* Start with the same capabilities as init but useless for doing
         * anything as the capabilities are bound to the new user namespace.
         */
	cred->securebits = SECUREBITS_DEFAULT;
	cred->cap_inheritable = CAP_EMPTY_SET;
	cred->cap_permitted = CAP_FULL_SET;
	cred->cap_effective = CAP_FULL_SET;
	cred->cap_ambient = CAP_EMPTY_SET;
	cred->cap_bset = CAP_FULL_SET;
#ifdef CONFIG_KEYS
	key_put(cred->request_key_auth);
	cred->request_key_auth = NULL;
#endif
	/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
	cred->user_ns = user_ns;
}

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/*
 * Create a new user namespace, deriving the creator from the user in the
 * passed credentials, and replacing that user with the new root user for the
 * new namespace.
 *
 * This is called by copy_creds(), which will finish setting the target task's
 * credentials.
 */


int create_user_ns(struct cred *new)
{
	struct user_namespace *ns, *parent_ns = new->user_ns;
	kuid_t owner = new->euid;
	kgid_t group = new->egid;
	struct ucounts *ucounts;
	int ret, i;

	ret = -ENOSPC;
	if (parent_ns->level > 32)
		goto fail;

	ucounts = inc_user_namespaces(parent_ns, owner);
	if (!ucounts)
		goto fail;

	/*
         * Verify that we can not violate the policy of which files
         * may be accessed that is specified by the root directory,
         * by verifing that the root directory is at the root of the
         * mount namespace which allows all files to be accessed.
         */
	ret = -EPERM;
	if (current_chrooted())
		goto fail_dec;

	/* The creator needs a mapping in the parent user namespace
         * or else we won't be able to reasonably tell userspace who
         * created a user_namespace.
         */
	ret = -EPERM;
	if (!kuid_has_mapping(parent_ns, owner) ||
	    !kgid_has_mapping(parent_ns, group))
		goto fail_dec;

	ret = -ENOMEM;
	ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
	if (!ns)
		goto fail_dec;

	ret = ns_alloc_inum(&ns->ns);
	if (ret)
		goto fail_free;
	ns->ns.ops = &userns_operations;

	atomic_set(&ns->count, 1);
	/* Leave the new->user_ns reference with the new user namespace. */
	ns->parent = parent_ns;
	ns->level = parent_ns->level + 1;
	ns->owner = owner;
	ns->group = group;
	INIT_WORK(&ns->work, free_user_ns);
	for (i = 0; i < UCOUNT_COUNTS; i++) {
		ns->ucount_max[i] = INT_MAX;
	}
	ns->ucounts = ucounts;

	/* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
	mutex_lock(&userns_state_mutex);
	ns->flags = parent_ns->flags;
	mutex_unlock(&userns_state_mutex);

#ifdef CONFIG_PERSISTENT_KEYRINGS
	init_rwsem(&ns->persistent_keyring_register_sem);
#endif
	ret = -ENOMEM;
	if (!setup_userns_sysctls(ns))
		goto fail_keyring;

	set_cred_user_ns(new, ns);
	return 0;
fail_keyring:
#ifdef CONFIG_PERSISTENT_KEYRINGS
	key_put(ns->persistent_keyring_register);
#endif
	ns_free_inum(&ns->ns);
fail_free:
	kmem_cache_free(user_ns_cachep, ns);
fail_dec:
	dec_user_namespaces(ucounts);
fail:
	return ret;
}

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int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
{
	struct cred *cred;
	int err = -ENOMEM;

	if (!(unshare_flags & CLONE_NEWUSER))
		return 0;

	cred = prepare_creds();
	if (cred) {
		err = create_user_ns(cred);
		if (err)
			put_cred(cred);
		else
			*new_cred = cred;
	}

	return err;
}

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static void free_user_ns(struct work_struct *work)
{
	struct user_namespace *parent, *ns =
		container_of(work, struct user_namespace, work);

	do {
		struct ucounts *ucounts = ns->ucounts;
		parent = ns->parent;
		if (ns->gid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
			kfree(ns->gid_map.forward);
			kfree(ns->gid_map.reverse);
		}
		if (ns->uid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
			kfree(ns->uid_map.forward);
			kfree(ns->uid_map.reverse);
		}
		if (ns->projid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
			kfree(ns->projid_map.forward);
			kfree(ns->projid_map.reverse);
		}
		retire_userns_sysctls(ns);
#ifdef CONFIG_PERSISTENT_KEYRINGS
		key_put(ns->persistent_keyring_register);
#endif
		ns_free_inum(&ns->ns);
		kmem_cache_free(user_ns_cachep, ns);
		dec_user_namespaces(ucounts);
		ns = parent;
	} while (atomic_dec_and_test(&parent->count));
}

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void __put_user_ns(struct user_namespace *ns)
{
	schedule_work(&ns->work);
}
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EXPORT_SYMBOL(__put_user_ns);

/**
 * idmap_key struct holds the information necessary to find an idmapping in a
 * sorted idmap array. It is passed to cmp_map_id() as first argument.
 */

struct idmap_key {
	
bool map_up; /* true  -> id from kid; false -> kid from id */
	
u32 id; /* id to find */
	
u32 count; /* == 0 unless used with map_id_range_down() */
};

/**
 * cmp_map_id - Function to be passed to bsearch() to find the requested
 * idmapping. Expects struct idmap_key to be passed via @k.
 */


static int cmp_map_id(const void *k, const void *e)
{
	u32 first, last, id2;
	const struct idmap_key *key = k;
	const struct uid_gid_extent *el = e;

	id2 = key->id + key->count - 1;

	/* handle map_id_{down,up}() */
	if (key->map_up)
		first = el->lower_first;
	else
		first = el->first;

	last = first + el->count - 1;

	if (key->id >= first && key->id <= last &&
	    (id2 >= first && id2 <= last))
		return 0;

	if (key->id < first || id2 < first)
		return -1;

	return 1;
}

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/**
 * map_id_range_down_max - Find idmap via binary search in ordered idmap array.
 * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
 */

static struct uid_gid_extent *

map_id_range_down_max(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
{
	struct idmap_key key;

	key.map_up = false;
	key.count = count;
	key.id = id;

	return bsearch(&key, map->forward, extents,
		       sizeof(struct uid_gid_extent), cmp_map_id);
}

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/**
 * map_id_range_down_base - Find idmap via binary search in static extent array.
 * Can only be called if number of mappings is equal or less than
 * UID_GID_MAP_MAX_BASE_EXTENTS.
 */

static struct uid_gid_extent *

map_id_range_down_base(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
{
	unsigned idx;
	u32 first, last, id2;

	id2 = id + count - 1;

	/* Find the matching extent */
	for (idx = 0; idx < extents; idx++) {
		first = map->extent[idx].first;
		last = first + map->extent[idx].count - 1;
		if (id >= first && id <= last &&
		    (id2 >= first && id2 <= last))
			return &map->extent[idx];
	}
	return NULL;
}

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static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
{
	struct uid_gid_extent *extent;
	unsigned extents = map->nr_extents;
	smp_rmb();

	if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
		extent = map_id_range_down_base(extents, map, id, count);
	else
		extent = map_id_range_down_max(extents, map, id, count);

	/* Map the id or note failure */
	if (extent)
		id = (id - extent->first) + extent->lower_first;
	else
		id = (u32) -1;

	return id;
}

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static u32 map_id_down(struct uid_gid_map *map, u32 id)
{
	return map_id_range_down(map, id, 1);
}

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/**
 * map_id_up_base - Find idmap via binary search in static extent array.
 * Can only be called if number of mappings is equal or less than
 * UID_GID_MAP_MAX_BASE_EXTENTS.
 */

static struct uid_gid_extent *

map_id_up_base(unsigned extents, struct uid_gid_map *map, u32 id)
{
	unsigned idx;
	u32 first, last;

	/* Find the matching extent */
	for (idx = 0; idx < extents; idx++) {
		first = map->extent[idx].lower_first;
		last = first + map->extent[idx].count - 1;
		if (id >= first && id <= last)
			return &map->extent[idx];
	}
	return NULL;
}

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/**
 * map_id_up_max - Find idmap via binary search in ordered idmap array.
 * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
 */

static struct uid_gid_extent *

map_id_up_max(unsigned extents, struct uid_gid_map *map, u32 id)
{
	struct idmap_key key;

	key.map_up = true;
	key.count = 1;
	key.id = id;

	return bsearch(&key, map->reverse, extents,
		       sizeof(struct uid_gid_extent), cmp_map_id);
}

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static u32 map_id_up(struct uid_gid_map *map, u32 id)
{
	struct uid_gid_extent *extent;
	unsigned extents = map->nr_extents;
	smp_rmb();

	if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
		extent = map_id_up_base(extents, map, id);
	else
		extent = map_id_up_max(extents, map, id);

	/* Map the id or note failure */
	if (extent)
		id = (id - extent->lower_first) + extent->first;
	else
		id = (u32) -1;

	return id;
}

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/**
 *      make_kuid - Map a user-namespace uid pair into a kuid.
 *      @ns:  User namespace that the uid is in
 *      @uid: User identifier
 *
 *      Maps a user-namespace uid pair into a kernel internal kuid,
 *      and returns that kuid.
 *
 *      When there is no mapping defined for the user-namespace uid
 *      pair INVALID_UID is returned.  Callers are expected to test
 *      for and handle INVALID_UID being returned.  INVALID_UID
 *      may be tested for using uid_valid().
 */


kuid_t make_kuid(struct user_namespace *ns, uid_t uid)
{
	/* Map the uid to a global kernel uid */
	return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
}
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EXPORT_SYMBOL(make_kuid);

/**
 *      from_kuid - Create a uid from a kuid user-namespace pair.
 *      @targ: The user namespace we want a uid in.
 *      @kuid: The kernel internal uid to start with.
 *
 *      Map @kuid into the user-namespace specified by @targ and
 *      return the resulting uid.
 *
 *      There is always a mapping into the initial user_namespace.
 *
 *      If @kuid has no mapping in @targ (uid_t)-1 is returned.
 */


uid_t from_kuid(struct user_namespace *targ, kuid_t kuid)
{
	/* Map the uid from a global kernel uid */
	return map_id_up(&targ->uid_map, __kuid_val(kuid));
}
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EXPORT_SYMBOL(from_kuid);

/**
 *      from_kuid_munged - Create a uid from a kuid user-namespace pair.
 *      @targ: The user namespace we want a uid in.
 *      @kuid: The kernel internal uid to start with.
 *
 *      Map @kuid into the user-namespace specified by @targ and
 *      return the resulting uid.
 *
 *      There is always a mapping into the initial user_namespace.
 *
 *      Unlike from_kuid from_kuid_munged never fails and always
 *      returns a valid uid.  This makes from_kuid_munged appropriate
 *      for use in syscalls like stat and getuid where failing the
 *      system call and failing to provide a valid uid are not an
 *      options.
 *
 *      If @kuid has no mapping in @targ overflowuid is returned.
 */


uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid)
{
	uid_t uid;
	uid = from_kuid(targ, kuid);

	if (uid == (uid_t) -1)
		uid = overflowuid;
	return uid;
}
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EXPORT_SYMBOL(from_kuid_munged);

/**
 *      make_kgid - Map a user-namespace gid pair into a kgid.
 *      @ns:  User namespace that the gid is in
 *      @gid: group identifier
 *
 *      Maps a user-namespace gid pair into a kernel internal kgid,
 *      and returns that kgid.
 *
 *      When there is no mapping defined for the user-namespace gid
 *      pair INVALID_GID is returned.  Callers are expected to test
 *      for and handle INVALID_GID being returned.  INVALID_GID may be
 *      tested for using gid_valid().
 */


kgid_t make_kgid(struct user_namespace *ns, gid_t gid)
{
	/* Map the gid to a global kernel gid */
	return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
}
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EXPORT_SYMBOL(make_kgid);

/**
 *      from_kgid - Create a gid from a kgid user-namespace pair.
 *      @targ: The user namespace we want a gid in.
 *      @kgid: The kernel internal gid to start with.
 *
 *      Map @kgid into the user-namespace specified by @targ and
 *      return the resulting gid.
 *
 *      There is always a mapping into the initial user_namespace.
 *
 *      If @kgid has no mapping in @targ (gid_t)-1 is returned.
 */


gid_t from_kgid(struct user_namespace *targ, kgid_t kgid)
{
	/* Map the gid from a global kernel gid */
	return map_id_up(&targ->gid_map, __kgid_val(kgid));
}
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EXPORT_SYMBOL(from_kgid);

/**
 *      from_kgid_munged - Create a gid from a kgid user-namespace pair.
 *      @targ: The user namespace we want a gid in.
 *      @kgid: The kernel internal gid to start with.
 *
 *      Map @kgid into the user-namespace specified by @targ and
 *      return the resulting gid.
 *
 *      There is always a mapping into the initial user_namespace.
 *
 *      Unlike from_kgid from_kgid_munged never fails and always
 *      returns a valid gid.  This makes from_kgid_munged appropriate
 *      for use in syscalls like stat and getgid where failing the
 *      system call and failing to provide a valid gid are not options.
 *
 *      If @kgid has no mapping in @targ overflowgid is returned.
 */


gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid)
{
	gid_t gid;
	gid = from_kgid(targ, kgid);

	if (gid == (gid_t) -1)
		gid = overflowgid;
	return gid;
}
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EXPORT_SYMBOL(from_kgid_munged);

/**
 *      make_kprojid - Map a user-namespace projid pair into a kprojid.
 *      @ns:  User namespace that the projid is in
 *      @projid: Project identifier
 *
 *      Maps a user-namespace uid pair into a kernel internal kuid,
 *      and returns that kuid.
 *
 *      When there is no mapping defined for the user-namespace projid
 *      pair INVALID_PROJID is returned.  Callers are expected to test
 *      for and handle handle INVALID_PROJID being returned.  INVALID_PROJID
 *      may be tested for using projid_valid().
 */


kprojid_t make_kprojid(struct user_namespace *ns, projid_t projid)
{
	/* Map the uid to a global kernel uid */
	return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid));
}
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EXPORT_SYMBOL(make_kprojid);

/**
 *      from_kprojid - Create a projid from a kprojid user-namespace pair.
 *      @targ: The user namespace we want a projid in.
 *      @kprojid: The kernel internal project identifier to start with.
 *
 *      Map @kprojid into the user-namespace specified by @targ and
 *      return the resulting projid.
 *
 *      There is always a mapping into the initial user_namespace.
 *
 *      If @kprojid has no mapping in @targ (projid_t)-1 is returned.
 */


projid_t from_kprojid(struct user_namespace *targ, kprojid_t kprojid)
{
	/* Map the uid from a global kernel uid */
	return map_id_up(&targ->projid_map, __kprojid_val(kprojid));
}
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EXPORT_SYMBOL(from_kprojid);

/**
 *      from_kprojid_munged - Create a projiid from a kprojid user-namespace pair.
 *      @targ: The user namespace we want a projid in.
 *      @kprojid: The kernel internal projid to start with.
 *
 *      Map @kprojid into the user-namespace specified by @targ and
 *      return the resulting projid.
 *
 *      There is always a mapping into the initial user_namespace.
 *
 *      Unlike from_kprojid from_kprojid_munged never fails and always
 *      returns a valid projid.  This makes from_kprojid_munged
 *      appropriate for use in syscalls like stat and where
 *      failing the system call and failing to provide a valid projid are
 *      not an options.
 *
 *      If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned.
 */


projid_t from_kprojid_munged(struct user_namespace *targ, kprojid_t kprojid)
{
	projid_t projid;
	projid = from_kprojid(targ, kprojid);

	if (projid == (projid_t) -1)
		projid = OVERFLOW_PROJID;
	return projid;
}
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EXPORT_SYMBOL(from_kprojid_munged);




static int uid_m_show(struct seq_file *seq, void *v)
{
	struct user_namespace *ns = seq->private;
	struct uid_gid_extent *extent = v;
	struct user_namespace *lower_ns;
	uid_t lower;

	lower_ns = seq_user_ns(seq);
	if ((lower_ns == ns) && lower_ns->parent)
		lower_ns = lower_ns->parent;

	lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first));

	seq_printf(seq, "%10u %10u %10u\n",
		extent->first,
		lower,
		extent->count);

	return 0;
}

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static int gid_m_show(struct seq_file *seq, void *v)
{
	struct user_namespace *ns = seq->private;
	struct uid_gid_extent *extent = v;
	struct user_namespace *lower_ns;
	gid_t lower;

	lower_ns = seq_user_ns(seq);
	if ((lower_ns == ns) && lower_ns->parent)
		lower_ns = lower_ns->parent;

	lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first));

	seq_printf(seq, "%10u %10u %10u\n",
		extent->first,
		lower,
		extent->count);

	return 0;
}

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static int projid_m_show(struct seq_file *seq, void *v)
{
	struct user_namespace *ns = seq->private;
	struct uid_gid_extent *extent = v;
	struct user_namespace *lower_ns;
	projid_t lower;

	lower_ns = seq_user_ns(seq);
	if ((lower_ns == ns) && lower_ns->parent)
		lower_ns = lower_ns->parent;

	lower = from_kprojid(lower_ns, KPROJIDT_INIT(extent->lower_first));

	seq_printf(seq, "%10u %10u %10u\n",
		extent->first,
		lower,
		extent->count);

	return 0;
}

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static void *m_start(struct seq_file *seq, loff_t *ppos,
		     struct uid_gid_map *map)
{
	loff_t pos = *ppos;
	unsigned extents = map->nr_extents;
	smp_rmb();

	if (pos >= extents)
		return NULL;

	if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
		return &map->extent[pos];

	return &map->forward[pos];
}

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static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
{
	struct user_namespace *ns = seq->private;

	return m_start(seq, ppos, &ns->uid_map);
}

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static void *gid_m_start(struct seq_file *seq, loff_t *ppos)
{
	struct user_namespace *ns = seq->private;

	return m_start(seq, ppos, &ns->gid_map);
}

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static void *projid_m_start(struct seq_file *seq, loff_t *ppos)
{
	struct user_namespace *ns = seq->private;

	return m_start(seq, ppos, &ns->projid_map);
}

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static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
{
	(*pos)++;
	return seq->op->start(seq, pos);
}

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static void m_stop(struct seq_file *seq, void *v)
{
	return;
}

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const struct seq_operations proc_uid_seq_operations = {
	.start = uid_m_start,
	.stop = m_stop,
	.next = m_next,
	.show = uid_m_show,
};


const struct seq_operations proc_gid_seq_operations = {
	.start = gid_m_start,
	.stop = m_stop,
	.next = m_next,
	.show = gid_m_show,
};


const struct seq_operations proc_projid_seq_operations = {
	.start = projid_m_start,
	.stop = m_stop,
	.next = m_next,
	.show = projid_m_show,
};



static bool mappings_overlap(struct uid_gid_map *new_map,
			     struct uid_gid_extent *extent)
{
	u32 upper_first, lower_first, upper_last, lower_last;
	unsigned idx;

	upper_first = extent->first;
	lower_first = extent->lower_first;
	upper_last = upper_first + extent->count - 1;
	lower_last = lower_first + extent->count - 1;

	for (idx = 0; idx < new_map->nr_extents; idx++) {
		u32 prev_upper_first, prev_lower_first;
		u32 prev_upper_last, prev_lower_last;
		struct uid_gid_extent *prev;

		if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
			prev = &new_map->extent[idx];
		else
			prev = &new_map->forward[idx];

		prev_upper_first = prev->first;
		prev_lower_first = prev->lower_first;
		prev_upper_last = prev_upper_first + prev->count - 1;
		prev_lower_last = prev_lower_first + prev->count - 1;

		/* Does the upper range intersect a previous extent? */