linux/security/keys/keyring.c
David Howells fd75815f72 KEYS: Add invalidation support
Add support for invalidating a key - which renders it immediately invisible to
further searches and causes the garbage collector to immediately wake up,
remove it from keyrings and then destroy it when it's no longer referenced.

It's better not to do this with keyctl_revoke() as that marks the key to start
returning -EKEYREVOKED to searches when what is actually desired is to have the
key refetched.

To invalidate a key the caller must be granted SEARCH permission by the key.
This may be too strict.  It may be better to also permit invalidation if the
caller has any of READ, WRITE or SETATTR permission.

The primary use for this is to evict keys that are cached in special keyrings,
such as the DNS resolver or an ID mapper.

Signed-off-by: David Howells <dhowells@redhat.com>
2012-05-11 10:56:56 +01:00

1279 lines
32 KiB
C

/* Keyring handling
*
* Copyright (C) 2004-2005, 2008 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/security.h>
#include <linux/seq_file.h>
#include <linux/err.h>
#include <keys/keyring-type.h>
#include <linux/uaccess.h>
#include "internal.h"
#define rcu_dereference_locked_keyring(keyring) \
(rcu_dereference_protected( \
(keyring)->payload.subscriptions, \
rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
#define rcu_deref_link_locked(klist, index, keyring) \
(rcu_dereference_protected( \
(klist)->keys[index], \
rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
#define MAX_KEYRING_LINKS \
min_t(size_t, USHRT_MAX - 1, \
((PAGE_SIZE - sizeof(struct keyring_list)) / sizeof(struct key *)))
#define KEY_LINK_FIXQUOTA 1UL
/*
* 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 key type definition. Keyrings are simply keys of this type and
* can be treated as ordinary keys in addition to having their own special
* operations.
*/
static int keyring_instantiate(struct key *keyring,
const void *data, size_t datalen);
static int keyring_match(const struct key *keyring, const void *criterion);
static void keyring_revoke(struct key *keyring);
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,
.match = keyring_match,
.revoke = keyring_revoke,
.destroy = keyring_destroy,
.describe = keyring_describe,
.read = keyring_read,
};
EXPORT_SYMBOL(key_type_keyring);
/*
* Semaphore to serialise link/link calls to prevent two link calls in parallel
* introducing a cycle.
*/
static DECLARE_RWSEM(keyring_serialise_link_sem);
/*
* Publish the name of a keyring so that it can be found by name (if it has
* one).
*/
static 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);
}
}
/*
* Initialise a keyring.
*
* Returns 0 on success, -EINVAL if 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;
}
/*
* Match keyrings on their name
*/
static int keyring_match(const struct key *keyring, const void *description)
{
return keyring->description &&
strcmp(keyring->description, description) == 0;
}
/*
* Clean up a keyring when it is destroyed. Unpublish its name if it had one
* and dispose of its data.
*
* The garbage collector detects the final key_put(), removes the keyring from
* the serial number tree and then does RCU synchronisation before coming here,
* so we shouldn't need to worry about code poking around here with the RCU
* readlock held by this time.
*/
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_access_pointer(keyring->payload.subscriptions);
if (klist) {
for (loop = klist->nkeys - 1; loop >= 0; loop--)
key_put(rcu_access_pointer(klist->keys[loop]));
kfree(klist);
}
}
/*
* Describe a keyring for /proc.
*/
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]");
if (key_is_instantiated(keyring)) {
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();
}
}
/*
* Read a list of key IDs from the keyring's contents in binary form
*
* The keyring's semaphore is read-locked by the caller.
*/
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_locked_keyring(keyring);
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 = rcu_deref_link_locked(klist, loop,
keyring);
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;
}
/*
* Allocate a keyring and link into the destination keyring.
*/
struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
const struct cred *cred, unsigned long flags,
struct key *dest)
{
struct key *keyring;
int ret;
keyring = key_alloc(&key_type_keyring, description,
uid, gid, cred,
(KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
flags);
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;
}
/**
* keyring_search_aux - Search a keyring tree for a key matching some criteria
* @keyring_ref: A pointer to the keyring with possession indicator.
* @cred: The credentials to use for permissions checks.
* @type: The type of key to search for.
* @description: Parameter for @match.
* @match: Function to rule on whether or not a key is the one required.
* @no_state_check: Don't check if a matching key is bad
*
* Search the supplied keyring tree for a key that matches the criteria given.
* The root keyring and any linked keyrings must grant Search permission to the
* caller to be searchable and keys can only be found if they too grant Search
* to the caller. The possession flag on the root keyring pointer controls use
* of the possessor bits in permissions checking of the entire tree. In
* addition, the LSM gets to forbid keyring searches and key matches.
*
* The search is performed as a breadth-then-depth search up to the prescribed
* limit (KEYRING_SEARCH_MAX_DEPTH).
*
* Keys are matched to the type provided and are then filtered by the match
* function, which is given the description to use in any way it sees fit. The
* match function may use any attributes of a key that it wishes to to
* determine the match. Normally the match function from the key type would be
* used.
*
* RCU is used to prevent the keyring key lists from disappearing without the
* need to take lots of locks.
*
* Returns a pointer to the found key and increments the key usage count if
* successful; -EAGAIN if no matching keys were found, or if expired or revoked
* keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
* specified keyring wasn't a keyring.
*
* In the case of a successful return, the possession attribute from
* @keyring_ref is propagated to the returned key reference.
*/
key_ref_t keyring_search_aux(key_ref_t keyring_ref,
const struct cred *cred,
struct key_type *type,
const void *description,
key_match_func_t match,
bool no_state_check)
{
struct {
/* Need a separate keylist pointer for RCU purposes */
struct key *keyring;
struct keyring_list *keylist;
int kix;
} stack[KEYRING_SEARCH_MAX_DEPTH];
struct keyring_list *keylist;
struct timespec now;
unsigned long possessed, kflags;
struct key *keyring, *key;
key_ref_t key_ref;
long err;
int sp, nkeys, 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 */
err = key_task_permission(keyring_ref, cred, KEY_SEARCH);
if (err < 0) {
key_ref = ERR_PTR(err);
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;
/* firstly we should check to see if this top-level keyring is what we
* are looking for */
key_ref = ERR_PTR(-EAGAIN);
kflags = keyring->flags;
if (keyring->type == type && match(keyring, description)) {
key = keyring;
if (no_state_check)
goto found;
/* check it isn't negative and hasn't expired or been
* revoked */
if (kflags & (1 << KEY_FLAG_REVOKED))
goto error_2;
if (key->expiry && now.tv_sec >= key->expiry)
goto error_2;
key_ref = ERR_PTR(key->type_data.reject_error);
if (kflags & (1 << KEY_FLAG_NEGATIVE))
goto error_2;
goto found;
}
/* otherwise, the top keyring must not be revoked, expired, or
* negatively instantiated if we are to search it */
key_ref = ERR_PTR(-EAGAIN);
if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
(1 << KEY_FLAG_REVOKED) |
(1 << KEY_FLAG_NEGATIVE)) ||
(keyring->expiry && now.tv_sec >= keyring->expiry))
goto error_2;
/* start processing a new keyring */
descend:
kflags = keyring->flags;
if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
(1 << KEY_FLAG_REVOKED)))
goto not_this_keyring;
keylist = rcu_dereference(keyring->payload.subscriptions);
if (!keylist)
goto not_this_keyring;
/* iterate through the keys in this keyring first */
nkeys = keylist->nkeys;
smp_rmb();
for (kix = 0; kix < nkeys; kix++) {
key = rcu_dereference(keylist->keys[kix]);
kflags = key->flags;
/* ignore keys not of this type */
if (key->type != type)
continue;
/* skip invalidated, revoked and expired keys */
if (!no_state_check) {
if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
(1 << KEY_FLAG_REVOKED)))
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),
cred, KEY_SEARCH) < 0)
continue;
if (no_state_check)
goto found;
/* we set a different error code if we pass a negative key */
if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
err = key->type_data.reject_error;
continue;
}
goto found;
}
/* search through the keyrings nested in this one */
kix = 0;
ascend:
nkeys = keylist->nkeys;
smp_rmb();
for (; kix < nkeys; kix++) {
key = rcu_dereference(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),
cred, KEY_SEARCH) < 0)
continue;
/* stack the current position */
stack[sp].keyring = keyring;
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--;
keyring = stack[sp].keyring;
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->last_used_at = now.tv_sec;
keyring->last_used_at = now.tv_sec;
while (sp > 0)
stack[--sp].keyring->last_used_at = now.tv_sec;
key_check(key);
key_ref = make_key_ref(key, possessed);
error_2:
rcu_read_unlock();
error:
return key_ref;
}
/**
* keyring_search - Search the supplied keyring tree for a matching key
* @keyring: The root of the keyring tree to be searched.
* @type: The type of keyring we want to find.
* @description: The name of the keyring we want to find.
*
* As keyring_search_aux() above, but using the current task's credentials and
* type's default matching function.
*/
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->cred,
type, description, type->match, false);
}
EXPORT_SYMBOL(keyring_search);
/*
* Search the given keyring only (no recursion).
*
* The caller must guarantee that the keyring is a keyring and that the
* permission is granted to search the keyring as no check is made here.
*
* RCU is used to make it unnecessary to lock the keyring key list here.
*
* Returns a pointer to the found key with usage count incremented if
* successful and returns -ENOKEY if not found. Revoked keys and keys not
* providing the requested permission are skipped over.
*
* If successful, the possession indicator is propagated from the keyring ref
* to the returned key reference.
*/
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 nkeys, 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) {
nkeys = klist->nkeys;
smp_rmb();
for (loop = 0; loop < nkeys ; loop++) {
key = rcu_dereference(klist->keys[loop]);
if (key->type == ktype &&
(!key->type->match ||
key->type->match(key, description)) &&
key_permission(make_key_ref(key, possessed),
perm) == 0 &&
!(key->flags & ((1 << KEY_FLAG_INVALIDATED) |
(1 << KEY_FLAG_REVOKED)))
)
goto found;
}
}
rcu_read_unlock();
return ERR_PTR(-ENOKEY);
found:
atomic_inc(&key->usage);
keyring->last_used_at = key->last_used_at =
current_kernel_time().tv_sec;
rcu_read_unlock();
return make_key_ref(key, possessed);
}
/*
* Find a keyring with the specified name.
*
* All named keyrings in the current user namespace are searched, provided they
* grant Search permission directly to the caller (unless this check is
* skipped). Keyrings whose usage points have reached zero or who have been
* revoked are skipped.
*
* Returns a pointer to the keyring with the keyring's refcount having being
* incremented on success. -ENOKEY is returned if a key could not be found.
*/
struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
{
struct key *keyring;
int bucket;
if (!name)
return ERR_PTR(-EINVAL);
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 (keyring->user->user_ns != current_user_ns())
continue;
if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
continue;
if (strcmp(keyring->description, name) != 0)
continue;
if (!skip_perm_check &&
key_permission(make_key_ref(keyring, 0),
KEY_SEARCH) < 0)
continue;
/* we've got a match but we might end up racing with
* key_cleanup() if the keyring is currently 'dead'
* (ie. it has a zero usage count) */
if (!atomic_inc_not_zero(&keyring->usage))
continue;
keyring->last_used_at = current_kernel_time().tv_sec;
goto out;
}
}
keyring = ERR_PTR(-ENOKEY);
out:
read_unlock(&keyring_name_lock);
return keyring;
}
/*
* 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, nkeys, 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 */
nkeys = keylist->nkeys;
smp_rmb();
for (; kix < nkeys; kix++) {
key = rcu_dereference(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;
}
/*
* 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);
if (klist->delkey != USHRT_MAX)
key_put(rcu_access_pointer(klist->keys[klist->delkey]));
kfree(klist);
}
/*
* Preallocate memory so that a key can be linked into to a keyring.
*/
int __key_link_begin(struct key *keyring, const struct key_type *type,
const char *description, unsigned long *_prealloc)
__acquires(&keyring->sem)
{
struct keyring_list *klist, *nklist;
unsigned long prealloc;
unsigned max;
time_t lowest_lru;
size_t size;
int loop, lru, ret;
kenter("%d,%s,%s,", key_serial(keyring), type->name, description);
if (keyring->type != &key_type_keyring)
return -ENOTDIR;
down_write(&keyring->sem);
ret = -EKEYREVOKED;
if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
goto error_krsem;
/* serialise link/link calls to prevent parallel calls causing a cycle
* when linking two keyring in opposite orders */
if (type == &key_type_keyring)
down_write(&keyring_serialise_link_sem);
klist = rcu_dereference_locked_keyring(keyring);
/* see if there's a matching key we can displace */
lru = -1;
if (klist && klist->nkeys > 0) {
lowest_lru = TIME_T_MAX;
for (loop = klist->nkeys - 1; loop >= 0; loop--) {
struct key *key = rcu_deref_link_locked(klist, loop,
keyring);
if (key->type == type &&
strcmp(key->description, description) == 0) {
/* Found a match - we'll replace the link with
* one to the new key. We record the slot
* position.
*/
klist->delkey = loop;
prealloc = 0;
goto done;
}
if (key->last_used_at < lowest_lru) {
lowest_lru = key->last_used_at;
lru = loop;
}
}
}
/* If the keyring is full then do an LRU discard */
if (klist &&
klist->nkeys == klist->maxkeys &&
klist->maxkeys >= MAX_KEYRING_LINKS) {
kdebug("LRU discard %d\n", lru);
klist->delkey = lru;
prealloc = 0;
goto done;
}
/* 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 error_sem;
if (klist && klist->nkeys < klist->maxkeys) {
/* there's sufficient slack space to append directly */
klist->delkey = klist->nkeys;
prealloc = KEY_LINK_FIXQUOTA;
} else {
/* grow the key list */
max = 4;
if (klist) {
max += klist->maxkeys;
if (max > MAX_KEYRING_LINKS)
max = MAX_KEYRING_LINKS;
BUG_ON(max <= klist->maxkeys);
}
size = sizeof(*klist) + sizeof(struct key *) * max;
ret = -ENOMEM;
nklist = kmalloc(size, GFP_KERNEL);
if (!nklist)
goto error_quota;
nklist->maxkeys = max;
if (klist) {
memcpy(nklist->keys, klist->keys,
sizeof(struct key *) * klist->nkeys);
nklist->delkey = klist->nkeys;
nklist->nkeys = klist->nkeys + 1;
klist->delkey = USHRT_MAX;
} else {
nklist->nkeys = 1;
nklist->delkey = 0;
}
/* add the key into the new space */
RCU_INIT_POINTER(nklist->keys[nklist->delkey], NULL);
prealloc = (unsigned long)nklist | KEY_LINK_FIXQUOTA;
}
done:
*_prealloc = prealloc;
kleave(" = 0");
return 0;
error_quota:
/* undo the quota changes */
key_payload_reserve(keyring,
keyring->datalen - KEYQUOTA_LINK_BYTES);
error_sem:
if (type == &key_type_keyring)
up_write(&keyring_serialise_link_sem);
error_krsem:
up_write(&keyring->sem);
kleave(" = %d", ret);
return ret;
}
/*
* Check already instantiated keys aren't going to be a problem.
*
* The caller must have called __key_link_begin(). Don't need to call this for
* keys that were created since __key_link_begin() was called.
*/
int __key_link_check_live_key(struct key *keyring, struct key *key)
{
if (key->type == &key_type_keyring)
/* check that we aren't going to create a cycle by linking one
* keyring to another */
return keyring_detect_cycle(keyring, key);
return 0;
}
/*
* Link a key into to a keyring.
*
* Must be called with __key_link_begin() having being called. Discards any
* already extant link to matching key if there is one, so that each keyring
* holds at most one link to any given key of a particular type+description
* combination.
*/
void __key_link(struct key *keyring, struct key *key,
unsigned long *_prealloc)
{
struct keyring_list *klist, *nklist;
struct key *discard;
nklist = (struct keyring_list *)(*_prealloc & ~KEY_LINK_FIXQUOTA);
*_prealloc = 0;
kenter("%d,%d,%p", keyring->serial, key->serial, nklist);
klist = rcu_dereference_locked_keyring(keyring);
atomic_inc(&key->usage);
keyring->last_used_at = key->last_used_at =
current_kernel_time().tv_sec;
/* there's a matching key we can displace or an empty slot in a newly
* allocated list we can fill */
if (nklist) {
kdebug("reissue %hu/%hu/%hu",
nklist->delkey, nklist->nkeys, nklist->maxkeys);
RCU_INIT_POINTER(nklist->keys[nklist->delkey], key);
rcu_assign_pointer(keyring->payload.subscriptions, nklist);
/* dispose of the old keyring list and, if there was one, the
* displaced key */
if (klist) {
kdebug("dispose %hu/%hu/%hu",
klist->delkey, klist->nkeys, klist->maxkeys);
call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
}
} else if (klist->delkey < klist->nkeys) {
kdebug("replace %hu/%hu/%hu",
klist->delkey, klist->nkeys, klist->maxkeys);
discard = rcu_dereference_protected(
klist->keys[klist->delkey],
rwsem_is_locked(&keyring->sem));
rcu_assign_pointer(klist->keys[klist->delkey], key);
/* The garbage collector will take care of RCU
* synchronisation */
key_put(discard);
} else {
/* there's sufficient slack space to append directly */
kdebug("append %hu/%hu/%hu",
klist->delkey, klist->nkeys, klist->maxkeys);
RCU_INIT_POINTER(klist->keys[klist->delkey], key);
smp_wmb();
klist->nkeys++;
}
}
/*
* Finish linking a key into to a keyring.
*
* Must be called with __key_link_begin() having being called.
*/
void __key_link_end(struct key *keyring, struct key_type *type,
unsigned long prealloc)
__releases(&keyring->sem)
{
BUG_ON(type == NULL);
BUG_ON(type->name == NULL);
kenter("%d,%s,%lx", keyring->serial, type->name, prealloc);
if (type == &key_type_keyring)
up_write(&keyring_serialise_link_sem);
if (prealloc) {
if (prealloc & KEY_LINK_FIXQUOTA)
key_payload_reserve(keyring,
keyring->datalen -
KEYQUOTA_LINK_BYTES);
kfree((struct keyring_list *)(prealloc & ~KEY_LINK_FIXQUOTA));
}
up_write(&keyring->sem);
}
/**
* key_link - Link a key to a keyring
* @keyring: The keyring to make the link in.
* @key: The key to link to.
*
* Make a link in a keyring to a key, such that the keyring holds a reference
* on that key and the key can potentially be found by searching that keyring.
*
* This function will write-lock the keyring's semaphore and will consume some
* of the user's key data quota to hold the link.
*
* Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring,
* -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is
* full, -EDQUOT if there is insufficient key data quota remaining to add
* another link or -ENOMEM if there's insufficient memory.
*
* It is assumed that the caller has checked that it is permitted for a link to
* be made (the keyring should have Write permission and the key Link
* permission).
*/
int key_link(struct key *keyring, struct key *key)
{
unsigned long prealloc;
int ret;
key_check(keyring);
key_check(key);
ret = __key_link_begin(keyring, key->type, key->description, &prealloc);
if (ret == 0) {
ret = __key_link_check_live_key(keyring, key);
if (ret == 0)
__key_link(keyring, key, &prealloc);
__key_link_end(keyring, key->type, prealloc);
}
return ret;
}
EXPORT_SYMBOL(key_link);
/**
* key_unlink - Unlink the first link to a key from a keyring.
* @keyring: The keyring to remove the link from.
* @key: The key the link is to.
*
* Remove a link from a keyring to a key.
*
* This function will write-lock the keyring's semaphore.
*
* Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if
* the key isn't linked to by the keyring or -ENOMEM if there's insufficient
* memory.
*
* It is assumed that the caller has checked that it is permitted for a link to
* be removed (the keyring should have Write permission; no permissions are
* required on the key).
*/
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 = rcu_dereference_locked_keyring(keyring);
if (klist) {
/* search the keyring for the key */
for (loop = 0; loop < klist->nkeys; loop++)
if (rcu_access_pointer(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;
}
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(rcu_access_pointer(klist->keys[loop]));
kfree(klist);
}
/**
* keyring_clear - Clear a keyring
* @keyring: The keyring to clear.
*
* Clear the contents of the specified keyring.
*
* Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring.
*/
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 = rcu_dereference_locked_keyring(keyring);
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;
}
EXPORT_SYMBOL(keyring_clear);
/*
* Dispose of the links from a revoked keyring.
*
* This is called with the key sem write-locked.
*/
static void keyring_revoke(struct key *keyring)
{
struct keyring_list *klist;
klist = rcu_dereference_locked_keyring(keyring);
/* adjust the quota */
key_payload_reserve(keyring, 0);
if (klist) {
rcu_assign_pointer(keyring->payload.subscriptions, NULL);
call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
}
}
/*
* Collect garbage from the contents of a keyring, replacing the old list with
* a new one with the pointers all shuffled down.
*
* Dead keys are classed as oned that are flagged as being dead or are revoked,
* expired or negative keys that were revoked or expired before the specified
* limit.
*/
void keyring_gc(struct key *keyring, time_t limit)
{
struct keyring_list *klist, *new;
struct key *key;
int loop, keep, max;
kenter("{%x,%s}", key_serial(keyring), keyring->description);
down_write(&keyring->sem);
klist = rcu_dereference_locked_keyring(keyring);
if (!klist)
goto no_klist;
/* work out how many subscriptions we're keeping */
keep = 0;
for (loop = klist->nkeys - 1; loop >= 0; loop--)
if (!key_is_dead(rcu_deref_link_locked(klist, loop, keyring),
limit))
keep++;
if (keep == klist->nkeys)
goto just_return;
/* allocate a new keyring payload */
max = roundup(keep, 4);
new = kmalloc(sizeof(struct keyring_list) + max * sizeof(struct key *),
GFP_KERNEL);
if (!new)
goto nomem;
new->maxkeys = max;
new->nkeys = 0;
new->delkey = 0;
/* install the live keys
* - must take care as expired keys may be updated back to life
*/
keep = 0;
for (loop = klist->nkeys - 1; loop >= 0; loop--) {
key = rcu_deref_link_locked(klist, loop, keyring);
if (!key_is_dead(key, limit)) {
if (keep >= max)
goto discard_new;
RCU_INIT_POINTER(new->keys[keep++], key_get(key));
}
}
new->nkeys = keep;
/* adjust the quota */
key_payload_reserve(keyring,
sizeof(struct keyring_list) +
KEYQUOTA_LINK_BYTES * keep);
if (keep == 0) {
rcu_assign_pointer(keyring->payload.subscriptions, NULL);
kfree(new);
} else {
rcu_assign_pointer(keyring->payload.subscriptions, new);
}
up_write(&keyring->sem);
call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
kleave(" [yes]");
return;
discard_new:
new->nkeys = keep;
keyring_clear_rcu_disposal(&new->rcu);
up_write(&keyring->sem);
kleave(" [discard]");
return;
just_return:
up_write(&keyring->sem);
kleave(" [no dead]");
return;
no_klist:
up_write(&keyring->sem);
kleave(" [no_klist]");
return;
nomem:
up_write(&keyring->sem);
kleave(" [oom]");
}