Commit message: KEYS: find_keyring_by_name() can gain access to a freed keyring

find_keyring_by_name() can gain access to a keyring that has had its reference
count reduced to zero, and is thus ready to be freed.  This then allows the
dead keyring to be brought back into use whilst it is being destroyed.

The following timeline illustrates the process:

|(cleaner)                           (user)
|
| free_user(user)                    sys_keyctl()
|  |                                  |
|  key_put(user->session_keyring)     keyctl_get_keyring_ID()
|  ||	//=> keyring->usage = 0        |
|  |schedule_work(&key_cleanup_task)   lookup_user_key()
|  ||                                   |
|  kmem_cache_free(,user)               |
|  .                                    |[KEY_SPEC_USER_KEYRING]
|  .                                    install_user_keyrings()
|  .                                    ||
| key_cleanup() [<= worker_thread()]    ||
|  |                                    ||
|  [spin_lock(&key_serial_lock)]        |[mutex_lock(&key_user_keyr..mutex)]
|  |                                    ||
|  atomic_read() == 0                   ||
|  |{ rb_ease(&key->serial_node,) }     ||
|  |                                    ||
|  [spin_unlock(&key_serial_lock)]      |find_keyring_by_name()
|  |                                    |||
|  keyring_destroy(keyring)             ||[read_lock(&keyring_name_lock)]
|  ||                                   |||
|  |[write_lock(&keyring_name_lock)]    ||atomic_inc(&keyring->usage)
|  |.                                   ||| *** GET freeing keyring ***
|  |.                                   ||[read_unlock(&keyring_name_lock)]
|  ||                                   ||
|  |list_del()                          |[mutex_unlock(&key_user_k..mutex)]
|  ||                                   |
|  |[write_unlock(&keyring_name_lock)]  ** INVALID keyring is returned **
|  |                                    .
|  kmem_cache_free(,keyring)            .
|                                       .
|                                       atomic_dec(&keyring->usage)
v                                         *** DESTROYED ***
TIME

If CONFIG_SLUB_DEBUG=y then we may see the following message generated:

	=============================================================================
	BUG key_jar: Poison overwritten
	-----------------------------------------------------------------------------

	INFO: 0xffff880197a7e200-0xffff880197a7e200. First byte 0x6a instead of 0x6b
	INFO: Allocated in key_alloc+0x10b/0x35f age=25 cpu=1 pid=5086
	INFO: Freed in key_cleanup+0xd0/0xd5 age=12 cpu=1 pid=10
	INFO: Slab 0xffffea000592cb90 objects=16 used=2 fp=0xffff880197a7e200 flags=0x200000000000c3
	INFO: Object 0xffff880197a7e200 @offset=512 fp=0xffff880197a7e300

	Bytes b4 0xffff880197a7e1f0:  5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
	  Object 0xffff880197a7e200:  6a 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b jkkkkkkkkkkkkkkk

Alternatively, we may see a system panic happen, such as:

	BUG: unable to handle kernel NULL pointer dereference at 0000000000000001
	IP: [<ffffffff810e61a3>] kmem_cache_alloc+0x5b/0xe9
	PGD 6b2b4067 PUD 6a80d067 PMD 0
	Oops: 0000 [#1] SMP
	last sysfs file: /sys/kernel/kexec_crash_loaded
	CPU 1
	...
	Pid: 31245, comm: su Not tainted 2.6.34-rc5-nofixed-nodebug #2 D2089/PRIMERGY
	RIP: 0010:[<ffffffff810e61a3>]  [<ffffffff810e61a3>] kmem_cache_alloc+0x5b/0xe9
	RSP: 0018:ffff88006af3bd98  EFLAGS: 00010002
	RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffff88007d19900b
	RDX: 0000000100000000 RSI: 00000000000080d0 RDI: ffffffff81828430
	RBP: ffffffff81828430 R08: ffff88000a293750 R09: 0000000000000000
	R10: 0000000000000001 R11: 0000000000100000 R12: 00000000000080d0
	R13: 00000000000080d0 R14: 0000000000000296 R15: ffffffff810f20ce
	FS:  00007f97116bc700(0000) GS:ffff88000a280000(0000) knlGS:0000000000000000
	CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
	CR2: 0000000000000001 CR3: 000000006a91c000 CR4: 00000000000006e0
	DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
	DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
	Process su (pid: 31245, threadinfo ffff88006af3a000, task ffff8800374414c0)
	Stack:
	 0000000512e0958e 0000000000008000 ffff880037f8d180 0000000000000001
	 0000000000000000 0000000000008001 ffff88007d199000 ffffffff810f20ce
	 0000000000008000 ffff88006af3be48 0000000000000024 ffffffff810face3
	Call Trace:
	 [<ffffffff810f20ce>] ? get_empty_filp+0x70/0x12f
	 [<ffffffff810face3>] ? do_filp_open+0x145/0x590
	 [<ffffffff810ce208>] ? tlb_finish_mmu+0x2a/0x33
	 [<ffffffff810ce43c>] ? unmap_region+0xd3/0xe2
	 [<ffffffff810e4393>] ? virt_to_head_page+0x9/0x2d
	 [<ffffffff81103916>] ? alloc_fd+0x69/0x10e
	 [<ffffffff810ef4ed>] ? do_sys_open+0x56/0xfc
	 [<ffffffff81008a02>] ? system_call_fastpath+0x16/0x1b
	Code: 0f 1f 44 00 00 49 89 c6 fa 66 0f 1f 44 00 00 65 4c 8b 04 25 60 e8 00 00 48 8b 45 00 49 01 c0 49 8b 18 48 85 db 74 0d 48 63 45 18 <48> 8b 04 03 49 89 00 eb 14 4c 89 f9 83 ca ff 44 89 e6 48 89 ef
	RIP  [<ffffffff810e61a3>] kmem_cache_alloc+0x5b/0xe9

This problem is that find_keyring_by_name does not confirm that the keyring is
valid before accepting it.

Skipping keyrings that have been reduced to a zero count seems the way to go.
To this end, use atomic_inc_not_zero() to increment the usage count and skip
the candidate keyring if that returns false.

The following script _may_ cause the bug to happen, but there's no guarantee
as the window of opportunity is small:

	#!/bin/sh
	LOOP=100000
	USER=dummy_user
	/bin/su -c "exit;" $USER || { /usr/sbin/adduser -m $USER; add=1; }
	for ((i=0; i<LOOP; i++))
	do
		/bin/su -c "echo '$i' > /dev/null" $USER
	done
	(( add == 1 )) && /usr/sbin/userdel -r $USER
	exit

Note that the nominated user must not be in use.

An alternative way of testing this may be:

	for ((i=0; i<100000; i++))
	do
		keyctl session foo /bin/true || break
	done >&/dev/null

as that uses a keyring named "foo" rather than relying on the user and
user-session named keyrings.

Reported-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
CVE: CVE-2010-1437
CWE: CWE-362
Vulnerability description: Race condition in the find_keyring_by_name function in security/keys/keyring.c in the Linux kernel 2.6.34-rc5 and earlier allows local users to cause a denial of service (memory corruption and system crash) or possibly have unspecified other impact via keyctl session commands that trigger access to a dead keyring that is undergoing deletion by the key_cleanup function.

Project: linux-2.6

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_check(keyring->payload.subscriptions,
				      rcu_read_lock_held() ||
				      atomic_read(&keyring->usage) == 0);
	if (klist) {
		for (loop = klist->nkeys - 1; loop >= 0; loop--)
			key_put(klist->keys[loop]);
		kfree(klist);
	}

} /* end keyring_destroy() */

Project: linux-2.6

static void keyring_revoke(struct key *keyring)
{
	struct keyring_list *klist = keyring->payload.subscriptions;

	/* 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);
	}

} /* end keyring_revoke() */

Project: linux-2.6

int __key_link(struct key *keyring, struct key *key)
{
	struct keyring_list *klist, *nklist;
	unsigned max;
	size_t size;
	int loop, 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;
	}

	/* see if there's a matching key we can displace */
	klist = keyring->payload.subscriptions;

	if (klist && klist->nkeys > 0) {
		struct key_type *type = key->type;

		for (loop = klist->nkeys - 1; loop >= 0; loop--) {
			if (klist->keys[loop]->type == type &&
			    strcmp(klist->keys[loop]->description,
				   key->description) == 0
			    ) {
				/* found a match - replace with new key */
				size = sizeof(struct key *) * klist->maxkeys;
				size += sizeof(*klist);
				BUG_ON(size > PAGE_SIZE);

				ret = -ENOMEM;
				nklist = kmemdup(klist, size, GFP_KERNEL);
				if (!nklist)
					goto error2;

				/* replace matched key */
				atomic_inc(&key->usage);
				nklist->keys[loop] = key;

				rcu_assign_pointer(
					keyring->payload.subscriptions,
					nklist);

				/* dispose of the old keyring list and the
				 * displaced key */
				klist->delkey = loop;
				call_rcu(&klist->rcu,
					 keyring_unlink_rcu_disposal);

				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 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();
	}
	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);
	}

done:
	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() */

Project: linux-2.6

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() */

Project: linux-2.6

static bool key_is_dead(struct key *key, time_t limit)
{
	return test_bit(KEY_FLAG_DEAD, &key->flags) ||
		(key->expiry > 0 && key->expiry <= limit);
}

Project: linux-2.6

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);

} /* end keyring_search() */

Project: linux-2.6

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() */

Project: linux-2.6
File: keyring.c

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);
}

Project: linux-2.6

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() */

Project: linux-2.6

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;
			goto out;
		}
	}

	keyring = ERR_PTR(-ENOKEY);
out:
	read_unlock(&keyring_name_lock);
	return keyring;

} /* end find_keyring_by_name() */

Project: linux-2.6

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 = 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() */

Project: linux-2.6

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() */

Project: linux-2.6

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() */

Project: linux-2.6

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;

} /* end keyring_alloc() */

Project: linux-2.6

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() */

Project: linux-2.6

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) == 0 &&
			    !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() */

Project: linux-2.6

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)
{
	struct {
		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, 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;

		/* 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(-ENOKEY);
		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_REVOKED) | (1 << KEY_FLAG_NEGATIVE)) ||
	    (keyring->expiry && now.tv_sec >= keyring->expiry))
		goto error_2;

	/* 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];
		kflags = key->flags;

		/* ignore keys not of this type */
		if (key->type != type)
			continue;

		/* skip revoked keys and expired keys */
		if (kflags & (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;

		/* we set a different error code if we pass a negative key */
		if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
			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),
					cred, KEY_SEARCH) < 0)
			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() */

Project: linux-2.6

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() */

Project: linux-2.6

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() */

Project: linux-2.6

static int keyring_match(const struct key *keyring, const void *description)
{
	return keyring->description &&
		strcmp(keyring->description, description) == 0;

} /* end keyring_match() */

Project: linux-2.6

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);
	}

} /* end keyring_publish_name() */

Project: linux-2.6

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 = keyring->payload.subscriptions;
	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(klist->keys[loop], 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 = klist->keys[loop];
		if (!key_is_dead(key, limit)) {
			if (keep >= max)
				goto discard_new;
			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]");
}

Project: linux-2.6

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() */