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keyctl.c
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keyctl.c
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/* keyctl.c: userspace keyctl operations
*
* Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* 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; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/keyctl.h>
#include <linux/fs.h>
#include <linux/capability.h>
#include <linux/string.h>
#include <linux/err.h>
#include <linux/vmalloc.h>
#include <linux/security.h>
#include <asm/uaccess.h>
#include "internal.h"
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
* - the keyring must be writable
* - returns the new key's serial number
* - implements add_key()
*/
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;
bool vm;
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 = strndup_user(_description, PAGE_SIZE);
if (IS_ERR(description)) {
ret = PTR_ERR(description);
goto error;
}
/* pull the payload in if one was supplied */
payload = NULL;
vm = false;
if (_payload) {
ret = -ENOMEM;
payload = kmalloc(plen, GFP_KERNEL);
if (!payload) {
if (plen <= PAGE_SIZE)
goto error2;
vm = true;
payload = vmalloc(plen);
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_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 (!vm)
kfree(payload);
else
vfree(payload);
error2:
kfree(description);
error:
return ret;
} /* end sys_add_key() */
/*****************************************************************************/
/*
* search the process keyrings for a matching key
* - nested keyrings may also be searched if they have Search permission
* - if a key is found, it will be attached to the destination keyring if
* there's one specified
* - /sbin/request-key will be invoked if _callout_info is non-NULL
* - the _callout_info string will be passed to /sbin/request-key
* - if the _callout_info string is empty, it will be rendered as "-"
* - implements request_key()
*/
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, PAGE_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_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, 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;
}
ret = key->serial;
key_put(key);
error5:
key_type_put(ktype);
error4:
key_ref_put(dest_ref);
error3:
kfree(callout_info);
error2:
kfree(description);
error:
return ret;
} /* end sys_request_key() */
/*****************************************************************************/
/*
* get the ID of the specified process keyring
* - the keyring must have search permission to be found
* - implements keyctl(KEYCTL_GET_KEYRING_ID)
*/
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_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;
} /* end keyctl_get_keyring_ID() */
/*****************************************************************************/
/*
* join the session keyring
* - implements keyctl(KEYCTL_JOIN_SESSION_KEYRING)
*/
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, PAGE_SIZE);
if (IS_ERR(name)) {
ret = PTR_ERR(name);
goto error;
}
}
/* join the session */
ret = join_session_keyring(name);
kfree(name);
error:
return ret;
} /* end keyctl_join_session_keyring() */
/*****************************************************************************/
/*
* update a key's data payload
* - the key must be writable
* - implements keyctl(KEYCTL_UPDATE)
*/
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 (_payload) {
ret = -ENOMEM;
payload = kmalloc(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_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:
kfree(payload);
error:
return ret;
} /* end keyctl_update_key() */
/*****************************************************************************/
/*
* revoke a key
* - the key must be writable
* - implements keyctl(KEYCTL_REVOKE)
*/
long keyctl_revoke_key(key_serial_t id)
{
key_ref_t key_ref;
long ret;
key_ref = lookup_user_key(id, 0, KEY_WRITE);
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
if (ret != -EACCES)
goto error;
key_ref = lookup_user_key(id, 0, KEY_SETATTR);
if (IS_ERR(key_ref)) {
ret = PTR_ERR(key_ref);
goto error;
}
}
key_revoke(key_ref_to_ptr(key_ref));
ret = 0;
key_ref_put(key_ref);
error:
return ret;
} /* end keyctl_revoke_key() */
/*****************************************************************************/
/*
* clear the specified process keyring
* - the keyring must be writable
* - implements keyctl(KEYCTL_CLEAR)
*/
long keyctl_keyring_clear(key_serial_t ringid)
{
key_ref_t keyring_ref;
long ret;
keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
if (IS_ERR(keyring_ref)) {
ret = PTR_ERR(keyring_ref);
goto error;
}
ret = keyring_clear(key_ref_to_ptr(keyring_ref));
key_ref_put(keyring_ref);
error:
return ret;
} /* end keyctl_keyring_clear() */
/*****************************************************************************/
/*
* link a key into a keyring
* - the keyring must be writable
* - the key must be linkable
* - implements keyctl(KEYCTL_LINK)
*/
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_WRITE);
if (IS_ERR(keyring_ref)) {
ret = PTR_ERR(keyring_ref);
goto error;
}
key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_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;
} /* end keyctl_keyring_link() */
/*****************************************************************************/
/*
* unlink the first attachment of a key from a keyring
* - the keyring must be writable
* - we don't need any permissions on the key
* - implements keyctl(KEYCTL_UNLINK)
*/
long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
{
key_ref_t keyring_ref, key_ref;
long ret;
keyring_ref = lookup_user_key(ringid, 0, KEY_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;
}
ret = key_unlink(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;
} /* end keyctl_keyring_unlink() */
/*****************************************************************************/
/*
* describe a user key
* - the key must have view permission
* - if there's a buffer, we place up to buflen bytes of data into it
* - unless there's an error, we return the amount of description available,
* irrespective of how much we may have copied
* - the description is formatted thus:
* type;uid;gid;perm;description<NUL>
* - implements keyctl(KEYCTL_DESCRIBE)
*/
long keyctl_describe_key(key_serial_t keyid,
char __user *buffer,
size_t buflen)
{
struct key *key, *instkey;
key_ref_t key_ref;
char *tmpbuf;
long ret;
key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_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:
/* calculate how much description we're going to return */
ret = -ENOMEM;
tmpbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!tmpbuf)
goto error2;
key = key_ref_to_ptr(key_ref);
ret = snprintf(tmpbuf, PAGE_SIZE - 1,
"%s;%d;%d;%08x;%s",
key->type->name,
key->uid,
key->gid,
key->perm,
key->description ?: "");
/* include a NUL char at the end of the data */
if (ret > PAGE_SIZE - 1)
ret = PAGE_SIZE - 1;
tmpbuf[ret] = 0;
ret++;
/* consider returning the data */
if (buffer && buflen > 0) {
if (buflen > ret)
buflen = ret;
if (copy_to_user(buffer, tmpbuf, buflen) != 0)
ret = -EFAULT;
}
kfree(tmpbuf);
error2:
key_ref_put(key_ref);
error:
return ret;
} /* end keyctl_describe_key() */
/*****************************************************************************/
/*
* search the specified keyring for a matching key
* - the start keyring must be searchable
* - nested keyrings may also be searched if they are searchable
* - only keys with search permission may be found
* - if a key is found, it will be attached to the destination keyring if
* there's one specified
* - implements keyctl(KEYCTL_SEARCH)
*/
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, PAGE_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_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_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);
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_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;
} /* end keyctl_keyring_search() */
/*****************************************************************************/
/*
* read a user key's payload
* - the keyring must be readable or the key must be searchable from the
* process's keyrings
* - if there's a buffer, we place up to buflen bytes of data into it
* - unless there's an error, we return the amount of data in the key,
* irrespective of how much we may have copied
* - implements keyctl(KEYCTL_READ)
*/
long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
{
struct key *key;
key_ref_t key_ref;
long ret;
/* find the key first */
key_ref = lookup_user_key(keyid, 0, 0);
if (IS_ERR(key_ref)) {
ret = -ENOKEY;
goto error;
}
key = key_ref_to_ptr(key_ref);
/* see if we can read it directly */
ret = key_permission(key_ref, KEY_READ);
if (ret == 0)
goto can_read_key;
if (ret != -EACCES)
goto error;
/* 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 error2;
}
/* the key is probably readable - now try to read it */
can_read_key:
ret = key_validate(key);
if (ret == 0) {
ret = -EOPNOTSUPP;
if (key->type->read) {
/* read the data with the semaphore held (since we
* might sleep) */
down_read(&key->sem);
ret = key->type->read(key, buffer, buflen);
up_read(&key->sem);
}
}
error2:
key_put(key);
error:
return ret;
} /* end keyctl_read_key() */
/*****************************************************************************/
/*
* change the ownership of a key
* - the keyring owned by the changer
* - if the uid or gid is -1, then that parameter is not changed
* - implements keyctl(KEYCTL_CHOWN)
*/
long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
{
struct key_user *newowner, *zapowner = NULL;
struct key *key;
key_ref_t key_ref;
long ret;
ret = 0;
if (uid == (uid_t) -1 && gid == (gid_t) -1)
goto error;
key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
KEY_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 (uid != (uid_t) -1 && 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 (gid != (gid_t) -1 && gid != key->gid && !in_group_p(gid))
goto error_put;
}
/* change the UID */
if (uid != (uid_t) -1 && uid != key->uid) {
ret = -ENOMEM;
newowner = key_user_lookup(uid, current_user_ns());
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 == 0) ?
key_quota_root_maxkeys : key_quota_maxkeys;
unsigned maxbytes = (uid == 0) ?
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 (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
atomic_dec(&key->user->nikeys);
atomic_inc(&newowner->nikeys);
}
zapowner = key->user;
key->user = newowner;
key->uid = uid;
}
/* change the GID */
if (gid != (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;
} /* end keyctl_chown_key() */
/*****************************************************************************/
/*
* change the permission mask on a key
* - the keyring owned by the changer
* - implements keyctl(KEYCTL_SETPERM)
*/
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_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) || key->uid == current_fsuid()) {
key->perm = perm;
ret = 0;
}
up_write(&key->sem);
key_put(key);
error:
return ret;
} /* end keyctl_setperm_key() */
/*
* get the destination keyring for instantiation
*/
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_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 the key with the specified payload, and, if one is given, link
* the key into the keyring
*/
long keyctl_instantiate_key(key_serial_t id,
const void __user *_payload,
size_t plen,
key_serial_t ringid)
{
const struct cred *cred = current_cred();
struct request_key_auth *rka;
struct key *instkey, *dest_keyring;
void *payload;
long ret;
bool vm = false;
kenter("%d,,%zu,%d", id, plen, ringid);
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;
if (rka->target_key->serial != id)
goto error;
/* pull the payload in if one was supplied */
payload = NULL;
if (_payload) {
ret = -ENOMEM;
payload = kmalloc(plen, GFP_KERNEL);
if (!payload) {
if (plen <= PAGE_SIZE)
goto error;
vm = true;
payload = vmalloc(plen);
if (!payload)
goto error;
}
ret = -EFAULT;
if (copy_from_user(payload, _payload, plen) != 0)
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 (!vm)
kfree(payload);
else
vfree(payload);
error:
return ret;
} /* end keyctl_instantiate_key() */
/*****************************************************************************/
/*
* negatively instantiate the key with the given timeout (in seconds), and, if
* one is given, link the key into the keyring
*/
long keyctl_negate_key(key_serial_t id, unsigned timeout, 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,%d", id, timeout, ringid);
/* 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;