path: root/kernel/user_namespace.c

// SPDX-License-Identifier: GPL-2.0-only

#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);
}

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

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;
}

/*
 * 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