android_kernel_xiaomi_sm8350/security/keys/keyring.c
David Howells 664cceb009 [PATCH] Keys: Add possessor permissions to keys [try #3]
The attached patch adds extra permission grants to keys for the possessor of a
key in addition to the owner, group and other permissions bits. This makes
SUID binaries easier to support without going as far as labelling keys and key
targets using the LSM facilities.

This patch adds a second "pointer type" to key structures (struct key_ref *)
that can have the bottom bit of the address set to indicate the possession of
a key. This is propagated through searches from the keyring to the discovered
key. It has been made a separate type so that the compiler can spot attempts
to dereference a potentially incorrect pointer.

The "possession" attribute can't be attached to a key structure directly as
it's not an intrinsic property of a key.

Pointers to keys have been replaced with struct key_ref *'s wherever
possession information needs to be passed through.

This does assume that the bottom bit of the pointer will always be zero on
return from kmem_cache_alloc().

The key reference type has been made into a typedef so that at least it can be
located in the sources, even though it's basically a pointer to an undefined
type. I've also renamed the accessor functions to be more useful, and all
reference variables should now end in "_ref".

Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-28 09:10:47 -07:00

1017 lines
24 KiB
C

/* keyring.c: keyring handling
*
* 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/seq_file.h>
#include <linux/err.h>
#include <asm/uaccess.h>
#include "internal.h"
/*
* when plumbing the depths of the key tree, this sets a hard limit set on how
* deep we're willing to go
*/
#define KEYRING_SEARCH_MAX_DEPTH 6
/*
* we keep all named keyrings in a hash to speed looking them up
*/
#define KEYRING_NAME_HASH_SIZE (1 << 5)
static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
static DEFINE_RWLOCK(keyring_name_lock);
static inline unsigned keyring_hash(const char *desc)
{
unsigned bucket = 0;
for (; *desc; desc++)
bucket += (unsigned char) *desc;
return bucket & (KEYRING_NAME_HASH_SIZE - 1);
}
/*
* the keyring type definition
*/
static int keyring_instantiate(struct key *keyring,
const void *data, size_t datalen);
static int keyring_duplicate(struct key *keyring, const struct key *source);
static int keyring_match(const struct key *keyring, const void *criterion);
static void keyring_destroy(struct key *keyring);
static void keyring_describe(const struct key *keyring, struct seq_file *m);
static long keyring_read(const struct key *keyring,
char __user *buffer, size_t buflen);
struct key_type key_type_keyring = {
.name = "keyring",
.def_datalen = sizeof(struct keyring_list),
.instantiate = keyring_instantiate,
.duplicate = keyring_duplicate,
.match = keyring_match,
.destroy = keyring_destroy,
.describe = keyring_describe,
.read = keyring_read,
};
/*
* semaphore to serialise link/link calls to prevent two link calls in parallel
* introducing a cycle
*/
DECLARE_RWSEM(keyring_serialise_link_sem);
/*****************************************************************************/
/*
* publish the name of a keyring so that it can be found by name (if it has
* one)
*/
void keyring_publish_name(struct key *keyring)
{
int bucket;
if (keyring->description) {
bucket = keyring_hash(keyring->description);
write_lock(&keyring_name_lock);
if (!keyring_name_hash[bucket].next)
INIT_LIST_HEAD(&keyring_name_hash[bucket]);
list_add_tail(&keyring->type_data.link,
&keyring_name_hash[bucket]);
write_unlock(&keyring_name_lock);
}
} /* end keyring_publish_name() */
/*****************************************************************************/
/*
* initialise a keyring
* - we object if we were given any data
*/
static int keyring_instantiate(struct key *keyring,
const void *data, size_t datalen)
{
int ret;
ret = -EINVAL;
if (datalen == 0) {
/* make the keyring available by name if it has one */
keyring_publish_name(keyring);
ret = 0;
}
return ret;
} /* end keyring_instantiate() */
/*****************************************************************************/
/*
* duplicate the list of subscribed keys from a source keyring into this one
*/
static int keyring_duplicate(struct key *keyring, const struct key *source)
{
struct keyring_list *sklist, *klist;
unsigned max;
size_t size;
int loop, ret;
const unsigned limit =
(PAGE_SIZE - sizeof(*klist)) / sizeof(struct key *);
ret = 0;
/* find out how many keys are currently linked */
rcu_read_lock();
sklist = rcu_dereference(source->payload.subscriptions);
max = 0;
if (sklist)
max = sklist->nkeys;
rcu_read_unlock();
/* allocate a new payload and stuff load with key links */
if (max > 0) {
BUG_ON(max > limit);
max = (max + 3) & ~3;
if (max > limit)
max = limit;
ret = -ENOMEM;
size = sizeof(*klist) + sizeof(struct key *) * max;
klist = kmalloc(size, GFP_KERNEL);
if (!klist)
goto error;
/* set links */
rcu_read_lock();
sklist = rcu_dereference(source->payload.subscriptions);
klist->maxkeys = max;
klist->nkeys = sklist->nkeys;
memcpy(klist->keys,
sklist->keys,
sklist->nkeys * sizeof(struct key *));
for (loop = klist->nkeys - 1; loop >= 0; loop--)
atomic_inc(&klist->keys[loop]->usage);
rcu_read_unlock();
rcu_assign_pointer(keyring->payload.subscriptions, klist);
ret = 0;
}
error:
return ret;
} /* end keyring_duplicate() */
/*****************************************************************************/
/*
* match keyrings on their name
*/
static int keyring_match(const struct key *keyring, const void *description)
{
return keyring->description &&
strcmp(keyring->description, description) == 0;
} /* end keyring_match() */
/*****************************************************************************/
/*
* dispose of the data dangling from the corpse of a keyring
*/
static void keyring_destroy(struct key *keyring)
{
struct keyring_list *klist;
int loop;
if (keyring->description) {
write_lock(&keyring_name_lock);
if (keyring->type_data.link.next != NULL &&
!list_empty(&keyring->type_data.link))
list_del(&keyring->type_data.link);
write_unlock(&keyring_name_lock);
}
klist = rcu_dereference(keyring->payload.subscriptions);
if (klist) {
for (loop = klist->nkeys - 1; loop >= 0; loop--)
key_put(klist->keys[loop]);
kfree(klist);
}
} /* end keyring_destroy() */
/*****************************************************************************/
/*
* describe the keyring
*/
static void keyring_describe(const struct key *keyring, struct seq_file *m)
{
struct keyring_list *klist;
if (keyring->description) {
seq_puts(m, keyring->description);
}
else {
seq_puts(m, "[anon]");
}
rcu_read_lock();
klist = rcu_dereference(keyring->payload.subscriptions);
if (klist)
seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
else
seq_puts(m, ": empty");
rcu_read_unlock();
} /* end keyring_describe() */
/*****************************************************************************/
/*
* read a list of key IDs from the keyring's contents
* - the keyring's semaphore is read-locked
*/
static long keyring_read(const struct key *keyring,
char __user *buffer, size_t buflen)
{
struct keyring_list *klist;
struct key *key;
size_t qty, tmp;
int loop, ret;
ret = 0;
klist = rcu_dereference(keyring->payload.subscriptions);
if (klist) {
/* calculate how much data we could return */
qty = klist->nkeys * sizeof(key_serial_t);
if (buffer && buflen > 0) {
if (buflen > qty)
buflen = qty;
/* copy the IDs of the subscribed keys into the
* buffer */
ret = -EFAULT;
for (loop = 0; loop < klist->nkeys; loop++) {
key = klist->keys[loop];
tmp = sizeof(key_serial_t);
if (tmp > buflen)
tmp = buflen;
if (copy_to_user(buffer,
&key->serial,
tmp) != 0)
goto error;
buflen -= tmp;
if (buflen == 0)
break;
buffer += tmp;
}
}
ret = qty;
}
error:
return ret;
} /* end keyring_read() */
/*****************************************************************************/
/*
* allocate a keyring and link into the destination keyring
*/
struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
int not_in_quota, struct key *dest)
{
struct key *keyring;
int ret;
keyring = key_alloc(&key_type_keyring, description,
uid, gid, KEY_POS_ALL | KEY_USR_ALL, not_in_quota);
if (!IS_ERR(keyring)) {
ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
if (ret < 0) {
key_put(keyring);
keyring = ERR_PTR(ret);
}
}
return keyring;
} /* end keyring_alloc() */
/*****************************************************************************/
/*
* search the supplied keyring tree for a key that matches the criterion
* - perform a breadth-then-depth search up to the prescribed limit
* - we only find keys on which we have search permission
* - we use the supplied match function to see if the description (or other
* feature of interest) matches
* - we rely on RCU to prevent the keyring lists from disappearing on us
* - we return -EAGAIN if we didn't find any matching key
* - we return -ENOKEY if we only found negative matching keys
* - we propagate the possession attribute from the keyring ref to the key ref
*/
key_ref_t keyring_search_aux(key_ref_t keyring_ref,
struct task_struct *context,
struct key_type *type,
const void *description,
key_match_func_t match)
{
struct {
struct keyring_list *keylist;
int kix;
} stack[KEYRING_SEARCH_MAX_DEPTH];
struct keyring_list *keylist;
struct timespec now;
unsigned long possessed;
struct key *keyring, *key;
key_ref_t key_ref;
long err;
int sp, kix;
keyring = key_ref_to_ptr(keyring_ref);
possessed = is_key_possessed(keyring_ref);
key_check(keyring);
/* top keyring must have search permission to begin the search */
key_ref = ERR_PTR(-EACCES);
if (!key_task_permission(keyring_ref, context, KEY_SEARCH))
goto error;
key_ref = ERR_PTR(-ENOTDIR);
if (keyring->type != &key_type_keyring)
goto error;
rcu_read_lock();
now = current_kernel_time();
err = -EAGAIN;
sp = 0;
/* start processing a new keyring */
descend:
if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
goto not_this_keyring;
keylist = rcu_dereference(keyring->payload.subscriptions);
if (!keylist)
goto not_this_keyring;
/* iterate through the keys in this keyring first */
for (kix = 0; kix < keylist->nkeys; kix++) {
key = keylist->keys[kix];
/* ignore keys not of this type */
if (key->type != type)
continue;
/* skip revoked keys and expired keys */
if (test_bit(KEY_FLAG_REVOKED, &key->flags))
continue;
if (key->expiry && now.tv_sec >= key->expiry)
continue;
/* keys that don't match */
if (!match(key, description))
continue;
/* key must have search permissions */
if (!key_task_permission(make_key_ref(key, possessed),
context, KEY_SEARCH))
continue;
/* we set a different error code if we find a negative key */
if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
err = -ENOKEY;
continue;
}
goto found;
}
/* search through the keyrings nested in this one */
kix = 0;
ascend:
for (; kix < keylist->nkeys; kix++) {
key = keylist->keys[kix];
if (key->type != &key_type_keyring)
continue;
/* recursively search nested keyrings
* - only search keyrings for which we have search permission
*/
if (sp >= KEYRING_SEARCH_MAX_DEPTH)
continue;
if (!key_task_permission(make_key_ref(key, possessed),
context, KEY_SEARCH))
continue;
/* stack the current position */
stack[sp].keylist = keylist;
stack[sp].kix = kix;
sp++;
/* begin again with the new keyring */
keyring = key;
goto descend;
}
/* the keyring we're looking at was disqualified or didn't contain a
* matching key */
not_this_keyring:
if (sp > 0) {
/* resume the processing of a keyring higher up in the tree */
sp--;
keylist = stack[sp].keylist;
kix = stack[sp].kix + 1;
goto ascend;
}
key_ref = ERR_PTR(err);
goto error_2;
/* we found a viable match */
found:
atomic_inc(&key->usage);
key_check(key);
key_ref = make_key_ref(key, possessed);
error_2:
rcu_read_unlock();
error:
return key_ref;
} /* end keyring_search_aux() */
/*****************************************************************************/
/*
* search the supplied keyring tree for a key that matches the criterion
* - perform a breadth-then-depth search up to the prescribed limit
* - we only find keys on which we have search permission
* - we readlock the keyrings as we search down the tree
* - we return -EAGAIN if we didn't find any matching key
* - we return -ENOKEY if we only found negative matching keys
*/
key_ref_t keyring_search(key_ref_t keyring,
struct key_type *type,
const char *description)
{
if (!type->match)
return ERR_PTR(-ENOKEY);
return keyring_search_aux(keyring, current,
type, description, type->match);
} /* end keyring_search() */
EXPORT_SYMBOL(keyring_search);
/*****************************************************************************/
/*
* search the given keyring only (no recursion)
* - keyring must be locked by caller
*/
key_ref_t __keyring_search_one(key_ref_t keyring_ref,
const struct key_type *ktype,
const char *description,
key_perm_t perm)
{
struct keyring_list *klist;
unsigned long possessed;
struct key *keyring, *key;
int loop;
keyring = key_ref_to_ptr(keyring_ref);
possessed = is_key_possessed(keyring_ref);
rcu_read_lock();
klist = rcu_dereference(keyring->payload.subscriptions);
if (klist) {
for (loop = 0; loop < klist->nkeys; loop++) {
key = klist->keys[loop];
if (key->type == ktype &&
(!key->type->match ||
key->type->match(key, description)) &&
key_permission(make_key_ref(key, possessed),
perm) &&
!test_bit(KEY_FLAG_REVOKED, &key->flags)
)
goto found;
}
}
rcu_read_unlock();
return ERR_PTR(-ENOKEY);
found:
atomic_inc(&key->usage);
rcu_read_unlock();
return make_key_ref(key, possessed);
} /* end __keyring_search_one() */
/*****************************************************************************/
/*
* search for an instantiation authorisation key matching a target key
* - the RCU read lock must be held by the caller
* - a target_id of zero specifies any valid token
*/
struct key *keyring_search_instkey(struct key *keyring,
key_serial_t target_id)
{
struct request_key_auth *rka;
struct keyring_list *klist;
struct key *instkey;
int loop;
klist = rcu_dereference(keyring->payload.subscriptions);
if (klist) {
for (loop = 0; loop < klist->nkeys; loop++) {
instkey = klist->keys[loop];
if (instkey->type != &key_type_request_key_auth)
continue;
rka = instkey->payload.data;
if (target_id && rka->target_key->serial != target_id)
continue;
/* the auth key is revoked during instantiation */
if (!test_bit(KEY_FLAG_REVOKED, &instkey->flags))
goto found;
instkey = ERR_PTR(-EKEYREVOKED);
goto error;
}
}
instkey = ERR_PTR(-EACCES);
goto error;
found:
atomic_inc(&instkey->usage);
error:
return instkey;
} /* end keyring_search_instkey() */
/*****************************************************************************/
/*
* find a keyring with the specified name
* - all named keyrings are searched
* - only find keyrings with search permission for the process
* - only find keyrings with a serial number greater than the one specified
*/
struct key *find_keyring_by_name(const char *name, key_serial_t bound)
{
struct key *keyring;
int bucket;
keyring = ERR_PTR(-EINVAL);
if (!name)
goto error;
bucket = keyring_hash(name);
read_lock(&keyring_name_lock);
if (keyring_name_hash[bucket].next) {
/* search this hash bucket for a keyring with a matching name
* that's readable and that hasn't been revoked */
list_for_each_entry(keyring,
&keyring_name_hash[bucket],
type_data.link
) {
if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
continue;
if (strcmp(keyring->description, name) != 0)
continue;
if (!key_permission(make_key_ref(keyring, 0),
KEY_SEARCH))
continue;
/* found a potential candidate, but we still need to
* check the serial number */
if (keyring->serial <= bound)
continue;
/* we've got a match */
atomic_inc(&keyring->usage);
read_unlock(&keyring_name_lock);
goto error;
}
}
read_unlock(&keyring_name_lock);
keyring = ERR_PTR(-ENOKEY);
error:
return keyring;
} /* end find_keyring_by_name() */
/*****************************************************************************/
/*
* see if a cycle will will be created by inserting acyclic tree B in acyclic
* tree A at the topmost level (ie: as a direct child of A)
* - since we are adding B to A at the top level, checking for cycles should
* just be a matter of seeing if node A is somewhere in tree B
*/
static int keyring_detect_cycle(struct key *A, struct key *B)
{
struct {
struct keyring_list *keylist;
int kix;
} stack[KEYRING_SEARCH_MAX_DEPTH];
struct keyring_list *keylist;
struct key *subtree, *key;
int sp, kix, ret;
rcu_read_lock();
ret = -EDEADLK;
if (A == B)
goto cycle_detected;
subtree = B;
sp = 0;
/* start processing a new keyring */
descend:
if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
goto not_this_keyring;
keylist = rcu_dereference(subtree->payload.subscriptions);
if (!keylist)
goto not_this_keyring;
kix = 0;
ascend:
/* iterate through the remaining keys in this keyring */
for (; kix < keylist->nkeys; kix++) {
key = keylist->keys[kix];
if (key == A)
goto cycle_detected;
/* recursively check nested keyrings */
if (key->type == &key_type_keyring) {
if (sp >= KEYRING_SEARCH_MAX_DEPTH)
goto too_deep;
/* stack the current position */
stack[sp].keylist = keylist;
stack[sp].kix = kix;
sp++;
/* begin again with the new keyring */
subtree = key;
goto descend;
}
}
/* the keyring we're looking at was disqualified or didn't contain a
* matching key */
not_this_keyring:
if (sp > 0) {
/* resume the checking of a keyring higher up in the tree */
sp--;
keylist = stack[sp].keylist;
kix = stack[sp].kix + 1;
goto ascend;
}
ret = 0; /* no cycles detected */
error:
rcu_read_unlock();
return ret;
too_deep:
ret = -ELOOP;
goto error;
cycle_detected:
ret = -EDEADLK;
goto error;
} /* end keyring_detect_cycle() */
/*****************************************************************************/
/*
* dispose of a keyring list after the RCU grace period
*/
static void keyring_link_rcu_disposal(struct rcu_head *rcu)
{
struct keyring_list *klist =
container_of(rcu, struct keyring_list, rcu);
kfree(klist);
} /* end keyring_link_rcu_disposal() */
/*****************************************************************************/
/*
* link a key into to a keyring
* - must be called with the keyring's semaphore write-locked
*/
int __key_link(struct key *keyring, struct key *key)
{
struct keyring_list *klist, *nklist;
unsigned max;
size_t size;
int ret;
ret = -EKEYREVOKED;
if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
goto error;
ret = -ENOTDIR;
if (keyring->type != &key_type_keyring)
goto error;
/* serialise link/link calls to prevent parallel calls causing a
* cycle when applied to two keyring in opposite orders */
down_write(&keyring_serialise_link_sem);
/* check that we aren't going to create a cycle adding one keyring to
* another */
if (key->type == &key_type_keyring) {
ret = keyring_detect_cycle(keyring, key);
if (ret < 0)
goto error2;
}
/* check that we aren't going to overrun the user's quota */
ret = key_payload_reserve(keyring,
keyring->datalen + KEYQUOTA_LINK_BYTES);
if (ret < 0)
goto error2;
klist = keyring->payload.subscriptions;
if (klist && klist->nkeys < klist->maxkeys) {
/* there's sufficient slack space to add directly */
atomic_inc(&key->usage);
klist->keys[klist->nkeys] = key;
smp_wmb();
klist->nkeys++;
smp_wmb();
ret = 0;
}
else {
/* grow the key list */
max = 4;
if (klist)
max += klist->maxkeys;
ret = -ENFILE;
if (max > 65535)
goto error3;
size = sizeof(*klist) + sizeof(struct key *) * max;
if (size > PAGE_SIZE)
goto error3;
ret = -ENOMEM;
nklist = kmalloc(size, GFP_KERNEL);
if (!nklist)
goto error3;
nklist->maxkeys = max;
nklist->nkeys = 0;
if (klist) {
nklist->nkeys = klist->nkeys;
memcpy(nklist->keys,
klist->keys,
sizeof(struct key *) * klist->nkeys);
}
/* add the key into the new space */
atomic_inc(&key->usage);
nklist->keys[nklist->nkeys++] = key;
rcu_assign_pointer(keyring->payload.subscriptions, nklist);
/* dispose of the old keyring list */
if (klist)
call_rcu(&klist->rcu, keyring_link_rcu_disposal);
ret = 0;
}
error2:
up_write(&keyring_serialise_link_sem);
error:
return ret;
error3:
/* undo the quota changes */
key_payload_reserve(keyring,
keyring->datalen - KEYQUOTA_LINK_BYTES);
goto error2;
} /* end __key_link() */
/*****************************************************************************/
/*
* link a key to a keyring
*/
int key_link(struct key *keyring, struct key *key)
{
int ret;
key_check(keyring);
key_check(key);
down_write(&keyring->sem);
ret = __key_link(keyring, key);
up_write(&keyring->sem);
return ret;
} /* end key_link() */
EXPORT_SYMBOL(key_link);
/*****************************************************************************/
/*
* dispose of a keyring list after the RCU grace period, freeing the unlinked
* key
*/
static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
{
struct keyring_list *klist =
container_of(rcu, struct keyring_list, rcu);
key_put(klist->keys[klist->delkey]);
kfree(klist);
} /* end keyring_unlink_rcu_disposal() */
/*****************************************************************************/
/*
* unlink the first link to a key from a keyring
*/
int key_unlink(struct key *keyring, struct key *key)
{
struct keyring_list *klist, *nklist;
int loop, ret;
key_check(keyring);
key_check(key);
ret = -ENOTDIR;
if (keyring->type != &key_type_keyring)
goto error;
down_write(&keyring->sem);
klist = keyring->payload.subscriptions;
if (klist) {
/* search the keyring for the key */
for (loop = 0; loop < klist->nkeys; loop++)
if (klist->keys[loop] == key)
goto key_is_present;
}
up_write(&keyring->sem);
ret = -ENOENT;
goto error;
key_is_present:
/* we need to copy the key list for RCU purposes */
nklist = kmalloc(sizeof(*klist) +
sizeof(struct key *) * klist->maxkeys,
GFP_KERNEL);
if (!nklist)
goto nomem;
nklist->maxkeys = klist->maxkeys;
nklist->nkeys = klist->nkeys - 1;
if (loop > 0)
memcpy(&nklist->keys[0],
&klist->keys[0],
loop * sizeof(struct key *));
if (loop < nklist->nkeys)
memcpy(&nklist->keys[loop],
&klist->keys[loop + 1],
(nklist->nkeys - loop) * sizeof(struct key *));
/* adjust the user's quota */
key_payload_reserve(keyring,
keyring->datalen - KEYQUOTA_LINK_BYTES);
rcu_assign_pointer(keyring->payload.subscriptions, nklist);
up_write(&keyring->sem);
/* schedule for later cleanup */
klist->delkey = loop;
call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
ret = 0;
error:
return ret;
nomem:
ret = -ENOMEM;
up_write(&keyring->sem);
goto error;
} /* end key_unlink() */
EXPORT_SYMBOL(key_unlink);
/*****************************************************************************/
/*
* dispose of a keyring list after the RCU grace period, releasing the keys it
* links to
*/
static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
{
struct keyring_list *klist;
int loop;
klist = container_of(rcu, struct keyring_list, rcu);
for (loop = klist->nkeys - 1; loop >= 0; loop--)
key_put(klist->keys[loop]);
kfree(klist);
} /* end keyring_clear_rcu_disposal() */
/*****************************************************************************/
/*
* clear the specified process keyring
* - implements keyctl(KEYCTL_CLEAR)
*/
int keyring_clear(struct key *keyring)
{
struct keyring_list *klist;
int ret;
ret = -ENOTDIR;
if (keyring->type == &key_type_keyring) {
/* detach the pointer block with the locks held */
down_write(&keyring->sem);
klist = keyring->payload.subscriptions;
if (klist) {
/* adjust the quota */
key_payload_reserve(keyring,
sizeof(struct keyring_list));
rcu_assign_pointer(keyring->payload.subscriptions,
NULL);
}
up_write(&keyring->sem);
/* free the keys after the locks have been dropped */
if (klist)
call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
ret = 0;
}
return ret;
} /* end keyring_clear() */
EXPORT_SYMBOL(keyring_clear);