// SPDX-License-Identifier: GPL-2.0-or-later
/* Userspace key control operations
 *
 * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/init.h>
#include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/key.h>
#include <linux/keyctl.h>
#include <linux/fs.h>
#include <linux/capability.h>
#include <linux/cred.h>
#include <linux/string.h>
#include <linux/err.h>
#include <linux/vmalloc.h>
#include <linux/security.h>
#include <linux/uio.h>
#include <linux/uaccess.h>
#include <keys/request_key_auth-type.h>
#include "internal.h"

#define KEY_MAX_DESC_SIZE 4096

static const unsigned char keyrings_capabilities[2] = {
        [0] = (KEYCTL_CAPS0_CAPABILITIES |
               (IS_ENABLED(CONFIG_PERSISTENT_KEYRINGS)  ? KEYCTL_CAPS0_PERSISTENT_KEYRINGS : 0) |
               (IS_ENABLED(CONFIG_KEY_DH_OPERATIONS)    ? KEYCTL_CAPS0_DIFFIE_HELLMAN : 0) |
               (IS_ENABLED(CONFIG_ASYMMETRIC_KEY_TYPE)  ? KEYCTL_CAPS0_PUBLIC_KEY : 0) |
               (IS_ENABLED(CONFIG_BIG_KEYS)             ? KEYCTL_CAPS0_BIG_KEY : 0) |
               KEYCTL_CAPS0_INVALIDATE |
               KEYCTL_CAPS0_RESTRICT_KEYRING |
               KEYCTL_CAPS0_MOVE
               ),
        [1] = (KEYCTL_CAPS1_NS_KEYRING_NAME |
               KEYCTL_CAPS1_NS_KEY_TAG),
};

static int key_get_type_from_user(char *type,
                                  const char __user *_type,
                                  unsigned len)
{
        int ret;

        ret = strncpy_from_user(type, _type, len);
        if (ret < 0)
                return ret;
        if (ret == 0 || ret >= len)
                return -EINVAL;
        if (type[0] == '.')
                return -EPERM;
        type[len - 1] = '\0';
        return 0;
}

/*
 * Extract the description of a new key from userspace and either add it as a
 * new key to the specified keyring or update a matching key in that keyring.
 *
 * If the description is NULL or an empty string, the key type is asked to
 * generate one from the payload.
 *
 * The keyring must be writable so that we can attach the key to it.
 *
 * If successful, the new key's serial number is returned, otherwise an error
 * code is returned.
 */
SYSCALL_DEFINE5(add_key, const char __user *, _type,
                const char __user *, _description,
                const void __user *, _payload,
                size_t, plen,
                key_serial_t, ringid)
{
        key_ref_t keyring_ref, key_ref;
        char type[32], *description;
        void *payload;
        long ret;

        ret = -EINVAL;
        if (plen > 1024 * 1024 - 1)
                goto error;

        /* draw all the data into kernel space */
        ret = key_get_type_from_user(type, _type, sizeof(type));
        if (ret < 0)
                goto error;

        description = NULL;
        if (_description) {
                description = strndup_user(_description, KEY_MAX_DESC_SIZE);
                if (IS_ERR(description)) {
                        ret = PTR_ERR(description);
                        goto error;
                }
                if (!*description) {
                        kfree(description);
                        description = NULL;
                } else if ((description[0] == '.') &&
                           (strncmp(type, "keyring", 7) == 0)) {
                        ret = -EPERM;
                        goto error2;
                }
        }

        /* pull the payload in if one was supplied */
        payload = NULL;

        if (plen) {
                ret = -ENOMEM;
                payload = kvmalloc(plen, GFP_KERNEL);
                if (!payload)
                        goto error2;

                ret = -EFAULT;
                if (copy_from_user(payload, _payload, plen) != 0)
                        goto error3;
        }

        /* find the target keyring (which must be writable) */
        keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
        if (IS_ERR(keyring_ref)) {
                ret = PTR_ERR(keyring_ref);
                goto error3;
        }

        /* create or update the requested key and add it to the target
         * keyring */
        key_ref = key_create_or_update(keyring_ref, type, description,
                                       payload, plen, KEY_PERM_UNDEF,
                                       KEY_ALLOC_IN_QUOTA);
        if (!IS_ERR(key_ref)) {
                ret = key_ref_to_ptr(key_ref)->serial;
                key_ref_put(key_ref);
        }
        else {
                ret = PTR_ERR(key_ref);
        }

        key_ref_put(keyring_ref);
 error3:
        if (payload) {
                memzero_explicit(payload, plen);
                kvfree(payload);
        }
 error2:
        kfree(description);
 error:
        return ret;
}

/*
 * Search the process keyrings and keyring trees linked from those for a
 * matching key.  Keyrings must have appropriate Search permission to be
 * searched.
 *
 * If a key is found, it will be attached to the destination keyring if there's
 * one specified and the serial number of the key will be returned.
 *
 * If no key is found, /sbin/request-key will be invoked if _callout_info is
 * non-NULL in an attempt to create a key.  The _callout_info string will be
 * passed to /sbin/request-key to aid with completing the request.  If the
 * _callout_info string is "" then it will be changed to "-".
 */
SYSCALL_DEFINE4(request_key, const char __user *, _type,
                const char __user *, _description,
                const char __user *, _callout_info,
                key_serial_t, destringid)
{
        struct key_type *ktype;
        struct key *key;
        key_ref_t dest_ref;
        size_t callout_len;
        char type[32], *description, *callout_info;
        long ret;

        /* pull the type into kernel space */
        ret = key_get_type_from_user(type, _type, sizeof(type));
        if (ret < 0)
                goto error;

        /* pull the description into kernel space */
        description = strndup_user(_description, KEY_MAX_DESC_SIZE);
        if (IS_ERR(description)) {
                ret = PTR_ERR(description);
                goto error;
        }

        /* pull the callout info into kernel space */
        callout_info = NULL;
        callout_len = 0;
        if (_callout_info) {
                callout_info = strndup_user(_callout_info, PAGE_SIZE);
                if (IS_ERR(callout_info)) {
                        ret = PTR_ERR(callout_info);
                        goto error2;
                }
                callout_len = strlen(callout_info);
        }

        /* get the destination keyring if specified */
        dest_ref = NULL;
        if (destringid) {
                dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
                                           KEY_NEED_WRITE);
                if (IS_ERR(dest_ref)) {
                        ret = PTR_ERR(dest_ref);
                        goto error3;
                }
        }

        /* find the key type */
        ktype = key_type_lookup(type);
        if (IS_ERR(ktype)) {
                ret = PTR_ERR(ktype);
                goto error4;
        }

        /* do the search */
        key = request_key_and_link(ktype, description, NULL, callout_info,
                                   callout_len, NULL, key_ref_to_ptr(dest_ref),
                                   KEY_ALLOC_IN_QUOTA);
        if (IS_ERR(key)) {
                ret = PTR_ERR(key);
                goto error5;
        }

        /* wait for the key to finish being constructed */
        ret = wait_for_key_construction(key, 1);
        if (ret < 0)
                goto error6;

        ret = key->serial;

error6:
        key_put(key);
error5:
        key_type_put(ktype);
error4:
        key_ref_put(dest_ref);
error3:
        kfree(callout_info);
error2:
        kfree(description);
error:
        return ret;
}

/*
 * Get the ID of the specified process keyring.
 *
 * The requested keyring must have search permission to be found.
 *
 * If successful, the ID of the requested keyring will be returned.
 */
long keyctl_get_keyring_ID(key_serial_t id, int create)
{
        key_ref_t key_ref;
        unsigned long lflags;
        long ret;

        lflags = create ? KEY_LOOKUP_CREATE : 0;
        key_ref = lookup_user_key(id, lflags, KEY_NEED_SEARCH);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error;
        }

        ret = key_ref_to_ptr(key_ref)->serial;
        key_ref_put(key_ref);
error:
        return ret;
}

/*
 * Join a (named) session keyring.
 *
 * Create and join an anonymous session keyring or join a named session
 * keyring, creating it if necessary.  A named session keyring must have Search
 * permission for it to be joined.  Session keyrings without this permit will
 * be skipped over.  It is not permitted for userspace to create or join
 * keyrings whose name begin with a dot.
 *
 * If successful, the ID of the joined session keyring will be returned.
 */
long keyctl_join_session_keyring(const char __user *_name)
{
        char *name;
        long ret;

        /* fetch the name from userspace */
        name = NULL;
        if (_name) {
                name = strndup_user(_name, KEY_MAX_DESC_SIZE);
                if (IS_ERR(name)) {
                        ret = PTR_ERR(name);
                        goto error;
                }

                ret = -EPERM;
                if (name[0] == '.')
                        goto error_name;
        }

        /* join the session */
        ret = join_session_keyring(name);
error_name:
        kfree(name);
error:
        return ret;
}

/*
 * Update a key's data payload from the given data.
 *
 * The key must grant the caller Write permission and the key type must support
 * updating for this to work.  A negative key can be positively instantiated
 * with this call.
 *
 * If successful, 0 will be returned.  If the key type does not support
 * updating, then -EOPNOTSUPP will be returned.
 */
long keyctl_update_key(key_serial_t id,
                       const void __user *_payload,
                       size_t plen)
{
        key_ref_t key_ref;
        void *payload;
        long ret;

        ret = -EINVAL;
        if (plen > PAGE_SIZE)
                goto error;

        /* pull the payload in if one was supplied */
        payload = NULL;
        if (plen) {
                ret = -ENOMEM;
                payload = kvmalloc(plen, GFP_KERNEL);
                if (!payload)
                        goto error;

                ret = -EFAULT;
                if (copy_from_user(payload, _payload, plen) != 0)
                        goto error2;
        }

        /* find the target key (which must be writable) */
        key_ref = lookup_user_key(id, 0, KEY_NEED_WRITE);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error2;
        }

        /* update the key */
        ret = key_update(key_ref, payload, plen);

        key_ref_put(key_ref);
error2:
        __kvzfree(payload, plen);
error:
        return ret;
}

/*
 * Revoke a key.
 *
 * The key must be grant the caller Write or Setattr permission for this to
 * work.  The key type should give up its quota claim when revoked.  The key
 * and any links to the key will be automatically garbage collected after a
 * certain amount of time (/proc/sys/kernel/keys/gc_delay).
 *
 * Keys with KEY_FLAG_KEEP set should not be revoked.
 *
 * If successful, 0 is returned.
 */
long keyctl_revoke_key(key_serial_t id)
{
        key_ref_t key_ref;
        struct key *key;
        long ret;

        key_ref = lookup_user_key(id, 0, KEY_NEED_WRITE);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                if (ret != -EACCES)
                        goto error;
                key_ref = lookup_user_key(id, 0, KEY_NEED_SETATTR);
                if (IS_ERR(key_ref)) {
                        ret = PTR_ERR(key_ref);
                        goto error;
                }
        }

        key = key_ref_to_ptr(key_ref);
        ret = 0;
        if (test_bit(KEY_FLAG_KEEP, &key->flags))
                ret = -EPERM;
        else
                key_revoke(key);

        key_ref_put(key_ref);
error:
        return ret;
}

/*
 * Invalidate a key.
 *
 * The key must be grant the caller Invalidate permission for this to work.
 * The key and any links to the key will be automatically garbage collected
 * immediately.
 *
 * Keys with KEY_FLAG_KEEP set should not be invalidated.
 *
 * If successful, 0 is returned.
 */
long keyctl_invalidate_key(key_serial_t id)
{
        key_ref_t key_ref;
        struct key *key;
        long ret;

        kenter("%d", id);

        key_ref = lookup_user_key(id, 0, KEY_NEED_SEARCH);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);

                /* Root is permitted to invalidate certain special keys */
                if (capable(CAP_SYS_ADMIN)) {
                        key_ref = lookup_user_key(id, 0, 0);
                        if (IS_ERR(key_ref))
                                goto error;
                        if (test_bit(KEY_FLAG_ROOT_CAN_INVAL,
                                     &key_ref_to_ptr(key_ref)->flags))
                                goto invalidate;
                        goto error_put;
                }

                goto error;
        }

invalidate:
        key = key_ref_to_ptr(key_ref);
        ret = 0;
        if (test_bit(KEY_FLAG_KEEP, &key->flags))
                ret = -EPERM;
        else
                key_invalidate(key);
error_put:
        key_ref_put(key_ref);
error:
        kleave(" = %ld", ret);
        return ret;
}

/*
 * Clear the specified keyring, creating an empty process keyring if one of the
 * special keyring IDs is used.
 *
 * The keyring must grant the caller Write permission and not have
 * KEY_FLAG_KEEP set for this to work.  If successful, 0 will be returned.
 */
long keyctl_keyring_clear(key_serial_t ringid)
{
        key_ref_t keyring_ref;
        struct key *keyring;
        long ret;

        keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
        if (IS_ERR(keyring_ref)) {
                ret = PTR_ERR(keyring_ref);

                /* Root is permitted to invalidate certain special keyrings */
                if (capable(CAP_SYS_ADMIN)) {
                        keyring_ref = lookup_user_key(ringid, 0, 0);
                        if (IS_ERR(keyring_ref))
                                goto error;
                        if (test_bit(KEY_FLAG_ROOT_CAN_CLEAR,
                                     &key_ref_to_ptr(keyring_ref)->flags))
                                goto clear;
                        goto error_put;
                }

                goto error;
        }

clear:
        keyring = key_ref_to_ptr(keyring_ref);
        if (test_bit(KEY_FLAG_KEEP, &keyring->flags))
                ret = -EPERM;
        else
                ret = keyring_clear(keyring);
error_put:
        key_ref_put(keyring_ref);
error:
        return ret;
}

/*
 * Create a link from a keyring to a key if there's no matching key in the
 * keyring, otherwise replace the link to the matching key with a link to the
 * new key.
 *
 * The key must grant the caller Link permission and the the keyring must grant
 * the caller Write permission.  Furthermore, if an additional link is created,
 * the keyring's quota will be extended.
 *
 * If successful, 0 will be returned.
 */
long keyctl_keyring_link(key_serial_t id, key_serial_t ringid)
{
        key_ref_t keyring_ref, key_ref;
        long ret;

        keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
        if (IS_ERR(keyring_ref)) {
                ret = PTR_ERR(keyring_ref);
                goto error;
        }

        key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_NEED_LINK);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error2;
        }

        ret = key_link(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));

        key_ref_put(key_ref);
error2:
        key_ref_put(keyring_ref);
error:
        return ret;
}

/*
 * Unlink a key from a keyring.
 *
 * The keyring must grant the caller Write permission for this to work; the key
 * itself need not grant the caller anything.  If the last link to a key is
 * removed then that key will be scheduled for destruction.
 *
 * Keys or keyrings with KEY_FLAG_KEEP set should not be unlinked.
 *
 * If successful, 0 will be returned.
 */
long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
{
        key_ref_t keyring_ref, key_ref;
        struct key *keyring, *key;
        long ret;

        keyring_ref = lookup_user_key(ringid, 0, KEY_NEED_WRITE);
        if (IS_ERR(keyring_ref)) {
                ret = PTR_ERR(keyring_ref);
                goto error;
        }

        key_ref = lookup_user_key(id, KEY_LOOKUP_FOR_UNLINK, 0);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error2;
        }

        keyring = key_ref_to_ptr(keyring_ref);
        key = key_ref_to_ptr(key_ref);
        if (test_bit(KEY_FLAG_KEEP, &keyring->flags) &&
            test_bit(KEY_FLAG_KEEP, &key->flags))
                ret = -EPERM;
        else
                ret = key_unlink(keyring, key);

        key_ref_put(key_ref);
error2:
        key_ref_put(keyring_ref);
error:
        return ret;
}

/*
 * Move a link to a key from one keyring to another, displacing any matching
 * key from the destination keyring.
 *
 * The key must grant the caller Link permission and both keyrings must grant
 * the caller Write permission.  There must also be a link in the from keyring
 * to the key.  If both keyrings are the same, nothing is done.
 *
 * If successful, 0 will be returned.
 */
long keyctl_keyring_move(key_serial_t id, key_serial_t from_ringid,
                         key_serial_t to_ringid, unsigned int flags)
{
        key_ref_t key_ref, from_ref, to_ref;
        long ret;

        if (flags & ~KEYCTL_MOVE_EXCL)
                return -EINVAL;

        key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_NEED_LINK);
        if (IS_ERR(key_ref))
                return PTR_ERR(key_ref);

        from_ref = lookup_user_key(from_ringid, 0, KEY_NEED_WRITE);
        if (IS_ERR(from_ref)) {
                ret = PTR_ERR(from_ref);
                goto error2;
        }

        to_ref = lookup_user_key(to_ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
        if (IS_ERR(to_ref)) {
                ret = PTR_ERR(to_ref);
                goto error3;
        }

        ret = key_move(key_ref_to_ptr(key_ref), key_ref_to_ptr(from_ref),
                       key_ref_to_ptr(to_ref), flags);

        key_ref_put(to_ref);
error3:
        key_ref_put(from_ref);
error2:
        key_ref_put(key_ref);
        return ret;
}

/*
 * Return a description of a key to userspace.
 *
 * The key must grant the caller View permission for this to work.
 *
 * If there's a buffer, we place up to buflen bytes of data into it formatted
 * in the following way:
 *
 *      type;uid;gid;perm;description<NUL>
 *
 * If successful, we return the amount of description available, irrespective
 * of how much we may have copied into the buffer.
 */
long keyctl_describe_key(key_serial_t keyid,
                         char __user *buffer,
                         size_t buflen)
{
        struct key *key, *instkey;
        key_ref_t key_ref;
        char *infobuf;
        long ret;
        int desclen, infolen;

        key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_NEED_VIEW);
        if (IS_ERR(key_ref)) {
                /* viewing a key under construction is permitted if we have the
                 * authorisation token handy */
                if (PTR_ERR(key_ref) == -EACCES) {
                        instkey = key_get_instantiation_authkey(keyid);
                        if (!IS_ERR(instkey)) {
                                key_put(instkey);
                                key_ref = lookup_user_key(keyid,
                                                          KEY_LOOKUP_PARTIAL,
                                                          0);
                                if (!IS_ERR(key_ref))
                                        goto okay;
                        }
                }

                ret = PTR_ERR(key_ref);
                goto error;
        }

okay:
        key = key_ref_to_ptr(key_ref);
        desclen = strlen(key->description);

        /* calculate how much information we're going to return */
        ret = -ENOMEM;
        infobuf = kasprintf(GFP_KERNEL,
                            "%s;%d;%d;%08x;",
                            key->type->name,
                            from_kuid_munged(current_user_ns(), key->uid),
                            from_kgid_munged(current_user_ns(), key->gid),
                            key->perm);
        if (!infobuf)
                goto error2;
        infolen = strlen(infobuf);
        ret = infolen + desclen + 1;

        /* consider returning the data */
        if (buffer && buflen >= ret) {
                if (copy_to_user(buffer, infobuf, infolen) != 0 ||
                    copy_to_user(buffer + infolen, key->description,
                                 desclen + 1) != 0)
                        ret = -EFAULT;
        }

        kfree(infobuf);
error2:
        key_ref_put(key_ref);
error:
        return ret;
}

/*
 * Search the specified keyring and any keyrings it links to for a matching
 * key.  Only keyrings that grant the caller Search permission will be searched
 * (this includes the starting keyring).  Only keys with Search permission can
 * be found.
 *
 * If successful, the found key will be linked to the destination keyring if
 * supplied and the key has Link permission, and the found key ID will be
 * returned.
 */
long keyctl_keyring_search(key_serial_t ringid,
                           const char __user *_type,
                           const char __user *_description,
                           key_serial_t destringid)
{
        struct key_type *ktype;
        key_ref_t keyring_ref, key_ref, dest_ref;
        char type[32], *description;
        long ret;

        /* pull the type and description into kernel space */
        ret = key_get_type_from_user(type, _type, sizeof(type));
        if (ret < 0)
                goto error;

        description = strndup_user(_description, KEY_MAX_DESC_SIZE);
        if (IS_ERR(description)) {
                ret = PTR_ERR(description);
                goto error;
        }

        /* get the keyring at which to begin the search */
        keyring_ref = lookup_user_key(ringid, 0, KEY_NEED_SEARCH);
        if (IS_ERR(keyring_ref)) {
                ret = PTR_ERR(keyring_ref);
                goto error2;
        }

        /* get the destination keyring if specified */
        dest_ref = NULL;
        if (destringid) {
                dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
                                           KEY_NEED_WRITE);
                if (IS_ERR(dest_ref)) {
                        ret = PTR_ERR(dest_ref);
                        goto error3;
                }
        }

        /* find the key type */
        ktype = key_type_lookup(type);
        if (IS_ERR(ktype)) {
                ret = PTR_ERR(ktype);
                goto error4;
        }

        /* do the search */
        key_ref = keyring_search(keyring_ref, ktype, description, true);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);

                /* treat lack or presence of a negative key the same */
                if (ret == -EAGAIN)
                        ret = -ENOKEY;
                goto error5;
        }

        /* link the resulting key to the destination keyring if we can */
        if (dest_ref) {
                ret = key_permission(key_ref, KEY_NEED_LINK);
                if (ret < 0)
                        goto error6;

                ret = key_link(key_ref_to_ptr(dest_ref), key_ref_to_ptr(key_ref));
                if (ret < 0)
                        goto error6;
        }

        ret = key_ref_to_ptr(key_ref)->serial;

error6:
        key_ref_put(key_ref);
error5:
        key_type_put(ktype);
error4:
        key_ref_put(dest_ref);
error3:
        key_ref_put(keyring_ref);
error2:
        kfree(description);
error:
        return ret;
}

/*
 * Call the read method
 */
static long __keyctl_read_key(struct key *key, char *buffer, size_t buflen)
{
        long ret;

        down_read(&key->sem);
        ret = key_validate(key);
        if (ret == 0)
                ret = key->type->read(key, buffer, buflen);
        up_read(&key->sem);
        return ret;
}

/*
 * Read a key's payload.
 *
 * The key must either grant the caller Read permission, or it must grant the
 * caller Search permission when searched for from the process keyrings.
 *
 * If successful, we place up to buflen bytes of data into the buffer, if one
 * is provided, and return the amount of data that is available in the key,
 * irrespective of how much we copied into the buffer.
 */
long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
{
        struct key *key;
        key_ref_t key_ref;
        long ret;
        char *key_data = NULL;
        size_t key_data_len;

        /* find the key first */
        key_ref = lookup_user_key(keyid, 0, 0);
        if (IS_ERR(key_ref)) {
                ret = -ENOKEY;
                goto out;
        }

        key = key_ref_to_ptr(key_ref);

        ret = key_read_state(key);
        if (ret < 0)
                goto key_put_out; /* Negatively instantiated */

        /* see if we can read it directly */
        ret = key_permission(key_ref, KEY_NEED_READ);
        if (ret == 0)
                goto can_read_key;
        if (ret != -EACCES)
                goto key_put_out;

        /* we can't; see if it's searchable from this process's keyrings
         * - we automatically take account of the fact that it may be
         *   dangling off an instantiation key
         */
        if (!is_key_possessed(key_ref)) {
                ret = -EACCES;
                goto key_put_out;
        }

        /* the key is probably readable - now try to read it */
can_read_key:
        if (!key->type->read) {
                ret = -EOPNOTSUPP;
                goto key_put_out;
        }

        if (!buffer || !buflen) {
                /* Get the key length from the read method */
                ret = __keyctl_read_key(key, NULL, 0);
                goto key_put_out;
        }

        /*
         * Read the data with the semaphore held (since we might sleep)
         * to protect against the key being updated or revoked.
         *
         * Allocating a temporary buffer to hold the keys before
         * transferring them to user buffer to avoid potential
         * deadlock involving page fault and mmap_sem.
         *
         * key_data_len = (buflen <= PAGE_SIZE)
         *              ? buflen : actual length of key data
         *
         * This prevents allocating arbitrary large buffer which can
         * be much larger than the actual key length. In the latter case,
         * at least 2 passes of this loop is required.
         */
        key_data_len = (buflen <= PAGE_SIZE) ? buflen : 0;
        for (;;) {
                if (key_data_len) {
                        key_data = kvmalloc(key_data_len, GFP_KERNEL);
                        if (!key_data) {
                                ret = -ENOMEM;
                                goto key_put_out;
                        }
                }

                ret = __keyctl_read_key(key, key_data, key_data_len);

                /*
                 * Read methods will just return the required length without
                 * any copying if the provided length isn't large enough.
                 */
                if (ret <= 0 || ret > buflen)
                        break;

                /*
                 * The key may change (unlikely) in between 2 consecutive
                 * __keyctl_read_key() calls. In this case, we reallocate
                 * a larger buffer and redo the key read when
                 * key_data_len < ret <= buflen.
                 */
                if (ret > key_data_len) {
                        if (unlikely(key_data))
                                __kvzfree(key_data, key_data_len);
                        key_data_len = ret;
                        continue;       /* Allocate buffer */
                }

                if (copy_to_user(buffer, key_data, ret))
                        ret = -EFAULT;
                break;
        }
        __kvzfree(key_data, key_data_len);

key_put_out:
        key_put(key);
out:
        return ret;
}

/*
 * Change the ownership of a key
 *
 * The key must grant the caller Setattr permission for this to work, though
 * the key need not be fully instantiated yet.  For the UID to be changed, or
 * for the GID to be changed to a group the caller is not a member of, the
 * caller must have sysadmin capability.  If either uid or gid is -1 then that
 * attribute is not changed.
 *
 * If the UID is to be changed, the new user must have sufficient quota to
 * accept the key.  The quota deduction will be removed from the old user to
 * the new user should the attribute be changed.
 *
 * If successful, 0 will be returned.
 */
long keyctl_chown_key(key_serial_t id, uid_t user, gid_t group)
{
        struct key_user *newowner, *zapowner = NULL;
        struct key *key;
        key_ref_t key_ref;
        long ret;
        kuid_t uid;
        kgid_t gid;

        uid = make_kuid(current_user_ns(), user);
        gid = make_kgid(current_user_ns(), group);
        ret = -EINVAL;
        if ((user != (uid_t) -1) && !uid_valid(uid))
                goto error;
        if ((group != (gid_t) -1) && !gid_valid(gid))
                goto error;

        ret = 0;
        if (user == (uid_t) -1 && group == (gid_t) -1)
                goto error;

        key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
                                  KEY_NEED_SETATTR);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error;
        }

        key = key_ref_to_ptr(key_ref);

        /* make the changes with the locks held to prevent chown/chown races */
        ret = -EACCES;
        down_write(&key->sem);

        if (!capable(CAP_SYS_ADMIN)) {
                /* only the sysadmin can chown a key to some other UID */
                if (user != (uid_t) -1 && !uid_eq(key->uid, uid))
                        goto error_put;

                /* only the sysadmin can set the key's GID to a group other
                 * than one of those that the current process subscribes to */
                if (group != (gid_t) -1 && !gid_eq(gid, key->gid) && !in_group_p(gid))
                        goto error_put;
        }

        /* change the UID */
        if (user != (uid_t) -1 && !uid_eq(uid, key->uid)) {
                ret = -ENOMEM;
                newowner = key_user_lookup(uid);
                if (!newowner)
                        goto error_put;

                /* transfer the quota burden to the new user */
                if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
                        unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
                                key_quota_root_maxkeys : key_quota_maxkeys;
                        unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
                                key_quota_root_maxbytes : key_quota_maxbytes;

                        spin_lock(&newowner->lock);
                        if (newowner->qnkeys + 1 > maxkeys ||
                            newowner->qnbytes + key->quotalen > maxbytes ||
                            newowner->qnbytes + key->quotalen <
                            newowner->qnbytes)
                                goto quota_overrun;

                        newowner->qnkeys++;
                        newowner->qnbytes += key->quotalen;
                        spin_unlock(&newowner->lock);

                        spin_lock(&key->user->lock);
                        key->user->qnkeys--;
                        key->user->qnbytes -= key->quotalen;
                        spin_unlock(&key->user->lock);
                }

                atomic_dec(&key->user->nkeys);
                atomic_inc(&newowner->nkeys);

                if (key->state != KEY_IS_UNINSTANTIATED) {
                        atomic_dec(&key->user->nikeys);
                        atomic_inc(&newowner->nikeys);
                }

                zapowner = key->user;
                key->user = newowner;
                key->uid = uid;
        }

        /* change the GID */
        if (group != (gid_t) -1)
                key->gid = gid;

        ret = 0;

error_put:
        up_write(&key->sem);
        key_put(key);
        if (zapowner)
                key_user_put(zapowner);
error:
        return ret;

quota_overrun:
        spin_unlock(&newowner->lock);
        zapowner = newowner;
        ret = -EDQUOT;
        goto error_put;
}

/*
 * Change the permission mask on a key.
 *
 * The key must grant the caller Setattr permission for this to work, though
 * the key need not be fully instantiated yet.  If the caller does not have
 * sysadmin capability, it may only change the permission on keys that it owns.
 */
long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
{
        struct key *key;
        key_ref_t key_ref;
        long ret;

        ret = -EINVAL;
        if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
                goto error;

        key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
                                  KEY_NEED_SETATTR);
        if (IS_ERR(key_ref)) {
                ret = PTR_ERR(key_ref);
                goto error;
        }

        key = key_ref_to_ptr(key_ref);

        /* make the changes with the locks held to prevent chown/chmod races */
        ret = -EACCES;
        down_write(&key->sem);

        /* if we're not the sysadmin, we can only change a key that we own */
        if (capable(CAP_SYS_ADMIN) || uid_eq(key->uid, current_fsuid())) {
                key->perm = perm;
                ret = 0;
        }

        up_write(&key->sem);
        key_put(key);
error:
        return ret;
}

/*
 * Get the destination keyring for instantiation and check that the caller has
 * Write permission on it.
 */
static long get_instantiation_keyring(key_serial_t ringid,
                                      struct request_key_auth *rka,
                                      struct key **_dest_keyring)
{
        key_ref_t dkref;

        *_dest_keyring = NULL;

        /* just return a NULL pointer if we weren't asked to make a link */
        if (ringid == 0)
                return 0;

        /* if a specific keyring is nominated by ID, then use that */
        if (ringid > 0) {
                dkref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
                if (IS_ERR(dkref))
                        return PTR_ERR(dkref);
                *_dest_keyring = key_ref_to_ptr(dkref);
                return 0;
        }

        if (ringid == KEY_SPEC_REQKEY_AUTH_KEY)
                return -EINVAL;

        /* otherwise specify the destination keyring recorded in the
         * authorisation key (any KEY_SPEC_*_KEYRING) */
        if (ringid >= KEY_SPEC_REQUESTOR_KEYRING) {
                *_dest_keyring = key_get(rka->dest_keyring);
                return 0;
        }

        return -ENOKEY;
}

/*
 * Change the request_key authorisation key on the current process.
 */
static int keyctl_change_reqkey_auth(struct key *key)
{
        struct cred *new;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;

        key_put(new->request_key_auth);
        new->request_key_auth = key_get(key);

        return commit_creds(new);
}

/*
 * Instantiate a key with the specified payload and link the key into the
 * destination keyring if one is given.
 *
 * The caller must have the appropriate instantiation permit set for this to
 * work (see keyctl_assume_authority).  No other permissions are required.
 *
 * If successful, 0 will be returned.
 */
long keyctl_instantiate_key_common(key_serial_t id,
                                   struct iov_iter *from,
                                   key_serial_t ringid)
{
        const struct cred *cred = current_cred();
        struct request_key_auth *rka;
        struct key *instkey, *dest_keyring;
        size_t plen = from ? iov_iter_count(from) : 0;
        void *payload;
        long ret;

        kenter("%d,,%zu,%d", id, plen, ringid);

        if (!plen)
                from = NULL;

        ret = -EINVAL;
        if (plen > 1024 * 1024 - 1)
                goto error;

        /* the appropriate instantiation authorisation key must have been
         * assumed before calling this */
        ret = -EPERM;
        instkey = cred->request_key_auth;
        if (!instkey)
                goto error;

        rka = instkey->payload.data[0];
        if (rka->target_key->serial != id)
                goto error;

        /* pull the payload in if one was supplied */
        payload = NULL;

        if (from) {
                ret = -ENOMEM;
                payload = kvmalloc(plen, GFP_KERNEL);
                if (!payload)
                        goto error;

                ret = -EFAULT;
                if (!copy_from_iter_full(payload, plen, from))
                        goto error2;
        }

        /* find the destination keyring amongst those belonging to the
         * requesting task */
        ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
        if (ret < 0)
                goto error2;

        /* instantiate the key and link it into a keyring */
        ret = key_instantiate_and_link(rka->target_key, payload, plen,
                                       dest_keyring, instkey);

        key_put(dest_keyring);

        /* discard the assumed authority if it's just been disabled by
         * instantiation of the key */
        if (ret == 0)
                keyctl_change_reqkey_auth(NULL);

error2:
        if (payload) {
                memzero_explicit(payload, plen);
                kvfree(payload);
        }
error:
        return ret;
}

/*
 * Instantiate a key with the specified payload and link the key into the
 * destination keyring if one is given.
 *
 * The caller must have the appropriate instantiation permit set for this to
 * work (see keyctl_assume_authority).  No other permissions are required.
 *
 * If successful, 0 will be returned.
 */
long keyctl_instantiate_key(key_serial_t id,
                            const void __user *_payload,
                            size_t plen,
                            key_serial_t ringid)
{
        if (_payload && plen) {
                struct iovec iov;
                struct iov_iter from;
                int ret;

                ret = import_single_range(WRITE, (void __user *)_payload, plen,
                                          &iov, &from);
                if (unlikely(ret))
                        return ret;

                return keyctl_instantiate_key_common(id, &from, ringid);
        }

        return keyctl_instantiate_key_common(id, NULL, ringid);
}

/*
 * Instantiate a key with the specified multipart payload and link the key into
 * the destination keyring if one is given.
 *
 * The caller must have the appropriate instantiation permit set for this to
 * work (see keyctl_assume_authority).  No other permissions are required.
 *
 * If successful, 0 will be returned.
 */
long keyctl_instantiate_key_iov(key_serial_t id,
                                const struct iovec __user *_payload_iov,
                                unsigned ioc,
                                key_serial_t ringid)
{
        struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
        struct iov_iter from;
        long ret;

        if (!_payload_iov)
                ioc = 0;

        ret = import_iovec(WRITE, _payload_iov, ioc,
                                    ARRAY_SIZE(iovstack), &iov, &from);
        if (ret < 0)
                return ret;
        ret = keyctl_instantiate_key_common(id, &from, ringid);
        kfree(iov);
        return ret;
}

/*
 * Negatively instantiate the key with the given timeout (in seconds) and link
 * the key into the destination keyring if one is given.
 *
 * The caller must have the appropriate instantiation permit set for this to
 * work (see keyctl_assume_authority).  No other permissions are required.
 *
 * The key and any links to the key will be automatically garbage collected
 * after the timeout expires.
 *
 * Negative keys are used to rate limit repeated request_key() calls by causing
 * them to return -ENOKEY until the negative key expires.
 *
 * If successful, 0 will be returned.
 */
long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
{
        return keyctl_reject_key(id, timeout, ENOKEY, ringid);
}

/*
 * Negatively instantiate the key with the given timeout (in seconds) and error
 * code and link the key into the destination keyring if one is given.
 *
 * The caller must have the appropriate instantiation permit set for this to
 * work (see keyctl_assume_authority).  No other permissions are required.
 *
 * The key and any links to the key will be automatically garbage collected
 * after the timeout expires.
 *
 * Negative keys are used to rate limit repeated request_key() calls by causing
 * them to return the specified error code until the negative key expires.
 *
 * If successful, 0 will be returned.
 */
long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
                       key_serial_t ringid)
{
        const struct cred *cred = current_cred();
        struct request_key_auth *rka;
        struct key *instkey, *dest_keyring;
        long ret;

        kenter("%d,%u,%u,%d", id, timeout, error, ringid);

        /* must be a valid error code and mustn't be a kernel special */
        if (error <= 0 ||
            error >= MAX_ERRNO ||
            error == ERESTARTSYS ||
            error == ERESTARTNOINTR ||
            error == ERESTARTNOHAND ||
            error == ERESTART_RESTARTBLOCK)
                return -EINVAL;

        /* the appropriate instantiation authorisation key must have been
         * assumed before calling this */
        ret = -EPERM;
        instkey = cred->request_key_auth;
        if (!instkey)
                goto error;

        rka = instkey->payload.data[0];
        if (rka->target_key->serial != id)
                goto error;

        /* find the destination keyring if present (which must also be
         * writable) */
        ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
        if (ret < 0)
                goto error;

        /* instantiate the key and link it into a keyring */
        ret = key_reject_and_link(rka->target_key, timeout, error,
                                  dest_keyring, instkey);

        key_put(dest_keyring);

        /* discard the assumed authority if it's just been disabled by
         * instantiation of the key */
        if (ret == 0)
                keyctl_change_reqkey_auth(NULL);

error:
        return ret;
}

/*
 * Read or set the default keyring in which request_key() will cache keys and
 * return the old setting.
 *
 * If a thread or process keyring is specified then it will be created if it
 * doesn't yet exist.  The old setting will be returned if successful.
 */
long keyctl_set_reqkey_keyring(int reqkey_defl)
{
        struct cred *new;
        int ret, old_setting;

        old_setting = current_cred_xxx(jit_keyring);

        if (reqkey_defl == KEY_REQKEY_DEFL_NO_CHANGE)
                return old_setting;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;

        switch (reqkey_defl) {
        case KEY_REQKEY_DEFL_THREAD_KEYRING:
                ret = install_thread_keyring_to_cred(new);
                if (ret < 0)
                        goto error;
                goto set;

        case KEY_REQKEY_DEFL_PROCESS_KEYRING:
                ret = install_process_keyring_to_cred(new);
                if (ret < 0)
                        goto error;
                goto set;

        case KEY_REQKEY_DEFL_DEFAULT:
        case KEY_REQKEY_DEFL_SESSION_KEYRING:
        case KEY_REQKEY_DEFL_USER_KEYRING:
        case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
        case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
                goto set;

        case KEY_REQKEY_DEFL_NO_CHANGE:
        case KEY_REQKEY_DEFL_GROUP_KEYRING:
        default:
                ret = -EINVAL;
                goto error;
        }

set:
        new->jit_keyring = reqkey_defl;
        commit_creds(new);
        return old_setting;
error:
        abort_creds(new);
        return ret;
}

/*
 * Set or clear the timeout on a key.
 *
 * Either the key must grant the caller Setattr permission or else the caller
 * must hold an instantiation authorisation token for the key.
 *
 * The timeout is either 0 to clear the timeout, or a number of seconds from
 * the current time.  The key and any links to the key will be automatically
 * garbage collected after the timeout expires.
 *
 * Keys with KEY_FLAG_KEEP set should not be timed out.
 *
 * If successful, 0 is returned.
 */
long keyctl_set_timeout(key_serial_t id, unsigned timeout)
{
        struct key *key, *instkey;
        key_ref_t key_ref;
        long ret;

        key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
                                  KEY_NEED_SETATTR);
        if (IS_ERR(key_ref)) {
                /* setting the timeout on a key under construction is permitted
                 * if we have the authorisation token handy */
                if (PTR_ERR(key_ref) == -EACCES) {
                        instkey = key_get_instantiation_authkey(id);
                        if (!IS_ERR(instkey)) {
                                key_put(instkey);
                                key_ref = lookup_user_key(id,
                                                          KEY_LOOKUP_PARTIAL,
                                                          0);
                                if (!IS_ERR(key_ref))
                                        goto okay;
                        }
                }

                ret = PTR_ERR(key_ref);
                goto error;
        }

okay:
        key = key_ref_to_ptr(key_ref);
        ret = 0;
        if (test_bit(KEY_FLAG_KEEP, &key->flags))
                ret = -EPERM;
        else
                key_set_timeout(key, timeout);
        key_put(key);

error:
        return ret;
}

/*
 * Assume (or clear) the authority to instantiate the specified key.
 *
 * This sets the authoritative token currently in force for key instantiation.
 * This must be done for a key to be instantiated.  It has the effect of making
 * available all the keys from the caller of the request_key() that created a
 * key to request_key() calls made by the caller of this function.
 *
 * The caller must have the instantiation key in their process keyrings with a
 * Search permission grant available to the caller.
 *
 * If the ID given is 0, then the setting will be cleared and 0 returned.
 *
 * If the ID given has a matching an authorisation key, then that key will be
 * set and its ID will be returned.  The authorisation key can be read to get
 * the callout information passed to request_key().
 */
long keyctl_assume_authority(key_serial_t id)
{
        struct key *authkey;
        long ret;

        /* special key IDs aren't permitted */
        ret = -EINVAL;
        if (id < 0)
                goto error;

        /* we divest ourselves of authority if given an ID of 0 */
        if (id == 0) {
                ret = keyctl_change_reqkey_auth(NULL);
                goto error;
        }

        /* attempt to assume the authority temporarily granted to us whilst we
         * instantiate the specified key
         * - the authorisation key must be in the current task's keyrings
         *   somewhere
         */
        authkey = key_get_instantiation_authkey(id);
        if (IS_ERR(authkey)) {
                ret = PTR_ERR(authkey);
                goto error;
        }

        ret = keyctl_change_reqkey_auth(authkey);
        if (ret == 0)
                ret = authkey->serial;
        key_put(authkey);
error:
        return ret;
}

/*
 * Get a key's the LSM security label.
 *
 * The key must grant the caller View permission for this to work.
 *
 * If there's a buffer, then up to buflen bytes of data will be placed into it.
 *
 * If successful, the amount of information available will be returned,
 * irrespective of how much was copied (including the terminal NUL).
 */
long keyctl_get_security(key_serial_t keyid,
                         char __user *buffer,
                         size_t buflen)
{
        struct key *key, *instkey;
        key_ref_t key_ref;
        char *context;
        long ret;

        key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_NEED_VIEW);
        if (IS_ERR(key_ref)) {
                if (PTR_ERR(key_ref) != -EACCES)
                        return PTR_ERR(key_ref);

                /* viewing a key under construction is also permitted if we
                 * have the authorisation token handy */
                instkey = key_get_instantiation_authkey(keyid);
                if (IS_ERR(instkey))
                        return PTR_ERR(instkey);
                key_put(instkey);

                key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, 0);
                if (IS_ERR(key_ref))
                        return PTR_ERR(key_ref);
        }

        key = key_ref_to_ptr(key_ref);
        ret = security_key_getsecurity(key, &context);
        if (ret == 0) {
                /* if no information was returned, give userspace an empty
                 * string */
                ret = 1;
                if (buffer && buflen > 0 &&
                    copy_to_user(buffer, "", 1) != 0)
                        ret = -EFAULT;
        } else if (ret > 0) {
                /* return as much data as there's room for */
                if (buffer && buflen > 0) {
                        if (buflen > ret)
                                buflen = ret;

                        if (copy_to_user(buffer, context, buflen) != 0)
                                ret = -EFAULT;
                }

                kfree(context);
        }

        key_ref_put(key_ref);
        return ret;
}

/*
 * Attempt to install the calling process's session keyring on the process's
 * parent process.
 *
 * The keyring must exist and must grant the caller LINK permission, and the
 * parent process must be single-threaded and must have the same effective
 * ownership as this process and mustn't be SUID/SGID.
 *
 * The keyring will be emplaced on the parent when it next resumes userspace.
 *
 * If successful, 0 will be returned.
 */
long keyctl_session_to_parent(void)
{
        struct task_struct *me, *parent;
        const struct cred *mycred, *pcred;
        struct callback_head *newwork, *oldwork;
        key_ref_t keyring_r;
        struct cred *cred;
        int ret;

        keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_NEED_LINK);
        if (IS_ERR(keyring_r))
                return PTR_ERR(keyring_r);

        ret = -ENOMEM;

        /* our parent is going to need a new cred struct, a new tgcred struct
         * and new security data, so we allocate them here to prevent ENOMEM in
         * our parent */
        cred = cred_alloc_blank();
        if (!cred)
                goto error_keyring;
        newwork = &cred->rcu;

        cred->session_keyring = key_ref_to_ptr(keyring_r);
        keyring_r = NULL;
        init_task_work(newwork, key_change_session_keyring);

        me = current;
        rcu_read_lock();
        write_lock_irq(&tasklist_lock);

        ret = -EPERM;
        oldwork = NULL;
        parent = rcu_dereference_protected(me->real_parent,
                                           lockdep_is_held(&tasklist_lock));

        /* the parent mustn't be init and mustn't be a kernel thread */
        if (parent->pid <= 1 || !parent->mm)
                goto unlock;

        /* the parent must be single threaded */
        if (!thread_group_empty(parent))
                goto unlock;

        /* the parent and the child must have different session keyrings or
         * there's no point */
        mycred = current_cred();
        pcred = __task_cred(parent);
        if (mycred == pcred ||
            mycred->session_keyring == pcred->session_keyring) {
                ret = 0;
                goto unlock;
        }

        /* the parent must have the same effective ownership and mustn't be
         * SUID/SGID */
        if (!uid_eq(pcred->uid,  mycred->euid) ||
            !uid_eq(pcred->euid, mycred->euid) ||
            !uid_eq(pcred->suid, mycred->euid) ||
            !gid_eq(pcred->gid,  mycred->egid) ||
            !gid_eq(pcred->egid, mycred->egid) ||
            !gid_eq(pcred->sgid, mycred->egid))
                goto unlock;

        /* the keyrings must have the same UID */
        if ((pcred->session_keyring &&
             !uid_eq(pcred->session_keyring->uid, mycred->euid)) ||
            !uid_eq(mycred->session_keyring->uid, mycred->euid))
                goto unlock;

        /* cancel an already pending keyring replacement */
        oldwork = task_work_cancel(parent, key_change_session_keyring);

        /* the replacement session keyring is applied just prior to userspace
         * restarting */
        ret = task_work_add(parent, newwork, true);
        if (!ret)
                newwork = NULL;
unlock:
        write_unlock_irq(&tasklist_lock);
        rcu_read_unlock();
        if (oldwork)
                put_cred(container_of(oldwork, struct cred, rcu));
        if (newwork)
                put_cred(cred);
        return ret;

error_keyring:
        key_ref_put(keyring_r);
        return ret;
}

/*
 * Apply a restriction to a given keyring.
 *
 * The caller must have Setattr permission to change keyring restrictions.
 *
 * The requested type name may be a NULL pointer to reject all attempts
 * to link to the keyring.  In this case, _restriction must also be NULL.
 * Otherwise, both _type and _restriction must be non-NULL.
 *
 * Returns 0 if successful.
 */
long keyctl_restrict_keyring(key_serial_t id, const char __user *_type,
                             const char __user *_restriction)
{
        key_ref_t key_ref;
        char type[32];
        char *restriction = NULL;
        long ret;

        key_ref = lookup_user_key(id, 0, KEY_NEED_SETATTR);
        if (IS_ERR(key_ref))
                return PTR_ERR(key_ref);

        ret = -EINVAL;
        if (_type) {
                if (!_restriction)
                        goto error;

                ret = key_get_type_from_user(type, _type, sizeof(type));
                if (ret < 0)
                        goto error;

                restriction = strndup_user(_restriction, PAGE_SIZE);
                if (IS_ERR(restriction)) {
                        ret = PTR_ERR(restriction);
                        goto error;
                }
        } else {
                if (_restriction)
                        goto error;
        }

        ret = keyring_restrict(key_ref, _type ? type : NULL, restriction);
        kfree(restriction);
error:
        key_ref_put(key_ref);
        return ret;
}

/*
 * Get keyrings subsystem capabilities.
 */
long keyctl_capabilities(unsigned char __user *_buffer, size_t buflen)
{
        size_t size = buflen;

        if (size > 0) {
                if (size > sizeof(keyrings_capabilities))
                        size = sizeof(keyrings_capabilities);
                if (copy_to_user(_buffer, keyrings_capabilities, size) != 0)
                        return -EFAULT;
                if (size < buflen &&
                    clear_user(_buffer + size, buflen - size) != 0)
                        return -EFAULT;
        }

        return sizeof(keyrings_capabilities);
}

/*
 * The key control system call
 */
SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
                unsigned long, arg4, unsigned long, arg5)
{
        switch (option) {
        case KEYCTL_GET_KEYRING_ID:
                return keyctl_get_keyring_ID((key_serial_t) arg2,
                                             (int) arg3);

        case KEYCTL_JOIN_SESSION_KEYRING:
                return keyctl_join_session_keyring((const char __user *) arg2);

        case KEYCTL_UPDATE:
                return keyctl_update_key((key_serial_t) arg2,
                                         (const void __user *) arg3,
                                         (size_t) arg4);

        case KEYCTL_REVOKE:
                return keyctl_revoke_key((key_serial_t) arg2);

        case KEYCTL_DESCRIBE:
                return keyctl_describe_key((key_serial_t) arg2,
                                           (char __user *) arg3,
                                           (unsigned) arg4);

        case KEYCTL_CLEAR:
                return keyctl_keyring_clear((key_serial_t) arg2);

        case KEYCTL_LINK:
                return keyctl_keyring_link((key_serial_t) arg2,
                                           (key_serial_t) arg3);

        case KEYCTL_UNLINK:
                return keyctl_keyring_unlink((key_serial_t) arg2,
                                             (key_serial_t) arg3);

        case KEYCTL_SEARCH:
                return keyctl_keyring_search((key_serial_t) arg2,
                                             (const char __user *) arg3,
                                             (const char __user *) arg4,
                                             (key_serial_t) arg5);

        case KEYCTL_READ:
                return keyctl_read_key((key_serial_t) arg2,
                                       (char __user *) arg3,
                                       (size_t) arg4);

        case KEYCTL_CHOWN:
                return keyctl_chown_key((key_serial_t) arg2,
                                        (uid_t) arg3,
                                        (gid_t) arg4);

        case KEYCTL_SETPERM:
                return keyctl_setperm_key((key_serial_t) arg2,
                                          (key_perm_t) arg3);

        case KEYCTL_INSTANTIATE:
                return keyctl_instantiate_key((key_serial_t) arg2,
                                              (const void __user *) arg3,
                                              (size_t) arg4,
                                              (key_serial_t) arg5);

        case KEYCTL_NEGATE:
                return keyctl_negate_key((key_serial_t) arg2,
                                         (unsigned) arg3,
                                         (key_serial_t) arg4);

        case KEYCTL_SET_REQKEY_KEYRING:
                return keyctl_set_reqkey_keyring(arg2);

        case KEYCTL_SET_TIMEOUT:
                return keyctl_set_timeout((key_serial_t) arg2,
                                          (unsigned) arg3);

        case KEYCTL_ASSUME_AUTHORITY:
                return keyctl_assume_authority((key_serial_t) arg2);

        case KEYCTL_GET_SECURITY:
                return keyctl_get_security((key_serial_t) arg2,
                                           (char __user *) arg3,
                                           (size_t) arg4);

        case KEYCTL_SESSION_TO_PARENT:
                return keyctl_session_to_parent();

        case KEYCTL_REJECT:
                return keyctl_reject_key((key_serial_t) arg2,
                                         (unsigned) arg3,
                                         (unsigned) arg4,
                                         (key_serial_t) arg5);

        case KEYCTL_INSTANTIATE_IOV:
                return keyctl_instantiate_key_iov(
                        (key_serial_t) arg2,
                        (const struct iovec __user *) arg3,
                        (unsigned) arg4,
                        (key_serial_t) arg5);

        case KEYCTL_INVALIDATE:
                return keyctl_invalidate_key((key_serial_t) arg2);

        case KEYCTL_GET_PERSISTENT:
                return keyctl_get_persistent((uid_t)arg2, (key_serial_t)arg3);

        case KEYCTL_DH_COMPUTE:
                return keyctl_dh_compute((struct keyctl_dh_params __user *) arg2,
                                         (char __user *) arg3, (size_t) arg4,
                                         (struct keyctl_kdf_params __user *) arg5);

        case KEYCTL_RESTRICT_KEYRING:
                return keyctl_restrict_keyring((key_serial_t) arg2,
                                               (const char __user *) arg3,
                                               (const char __user *) arg4);

        case KEYCTL_PKEY_QUERY:
                if (arg3 != 0)
                        return -EINVAL;
                return keyctl_pkey_query((key_serial_t)arg2,
                                         (const char __user *)arg4,
                                         (struct keyctl_pkey_query __user *)arg5);

        case KEYCTL_PKEY_ENCRYPT:
        case KEYCTL_PKEY_DECRYPT:
        case KEYCTL_PKEY_SIGN:
                return keyctl_pkey_e_d_s(
                        option,
                        (const struct keyctl_pkey_params __user *)arg2,
                        (const char __user *)arg3,
                        (const void __user *)arg4,
                        (void __user *)arg5);

        case KEYCTL_PKEY_VERIFY:
                return keyctl_pkey_verify(
                        (const struct keyctl_pkey_params __user *)arg2,
                        (const char __user *)arg3,
                        (const void __user *)arg4,
                        (const void __user *)arg5);

        case KEYCTL_MOVE:
                return keyctl_keyring_move((key_serial_t)arg2,
                                           (key_serial_t)arg3,
                                           (key_serial_t)arg4,
                                           (unsigned int)arg5);

        case KEYCTL_CAPABILITIES:
                return keyctl_capabilities((unsigned char __user *)arg2, (size_t)arg3);

        default:
                return -EOPNOTSUPP;
        }
}