[mirror_ubuntu-jammy-kernel.git] / security / keys / gc.c

/* Key garbage collector
 *
 * Copyright (C) 2009-2011 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 Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <keys/keyring-type.h>
#include "internal.h"

/*
 * Delay between key revocation/expiry in seconds
 */
unsigned key_gc_delay = 5 * 60;

/*
 * Reaper for unused keys.
 */
static void key_garbage_collector(struct work_struct *work);
DECLARE_WORK(key_gc_work, key_garbage_collector);

/*
 * Reaper for links from keyrings to dead keys.
 */
static void key_gc_timer_func(unsigned long);
static DEFINE_TIMER(key_gc_timer, key_gc_timer_func, 0, 0);

static time_t key_gc_next_run = LONG_MAX;
static struct key_type *key_gc_dead_keytype;

static unsigned long key_gc_flags;
#define KEY_GC_KEY_EXPIRED	0	/* A key expired and needs unlinking */
#define KEY_GC_REAP_KEYTYPE	1	/* A keytype is being unregistered */
#define KEY_GC_REAPING_KEYTYPE	2	/* Cleared when keytype reaped */


/*
 * Any key whose type gets unregistered will be re-typed to this if it can't be
 * immediately unlinked.
 */
struct key_type key_type_dead = {
	.name = "dead",
};

/*
 * Schedule a garbage collection run.
 * - time precision isn't particularly important
 */
void key_schedule_gc(time_t gc_at)
{
	unsigned long expires;
	time_t now = current_kernel_time().tv_sec;

	kenter("%ld", gc_at - now);

	if (gc_at <= now || test_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags)) {
		kdebug("IMMEDIATE");
		schedule_work(&key_gc_work);
	} else if (gc_at < key_gc_next_run) {
		kdebug("DEFERRED");
		key_gc_next_run = gc_at;
		expires = jiffies + (gc_at - now) * HZ;
		mod_timer(&key_gc_timer, expires);
	}
}

/*
 * Schedule a dead links collection run.
 */
void key_schedule_gc_links(void)
{
	set_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags);
	schedule_work(&key_gc_work);
}

/*
 * Some key's cleanup time was met after it expired, so we need to get the
 * reaper to go through a cycle finding expired keys.
 */
static void key_gc_timer_func(unsigned long data)
{
	kenter("");
	key_gc_next_run = LONG_MAX;
	key_schedule_gc_links();
}

/*
 * wait_on_bit() sleep function for uninterruptible waiting
 */
static int key_gc_wait_bit(void *flags)
{
	schedule();
	return 0;
}

/*
 * Reap keys of dead type.
 *
 * We use three flags to make sure we see three complete cycles of the garbage
 * collector: the first to mark keys of that type as being dead, the second to
 * collect dead links and the third to clean up the dead keys.  We have to be
 * careful as there may already be a cycle in progress.
 *
 * The caller must be holding key_types_sem.
 */
void key_gc_keytype(struct key_type *ktype)
{
	kenter("%s", ktype->name);

	key_gc_dead_keytype = ktype;
	set_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags);
	smp_mb();
	set_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags);

	kdebug("schedule");
	schedule_work(&key_gc_work);

	kdebug("sleep");
	wait_on_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE, key_gc_wait_bit,
		    TASK_UNINTERRUPTIBLE);

	key_gc_dead_keytype = NULL;
	kleave("");
}

static int key_gc_keyring_func(const void *object, void *iterator_data)
{
	const struct key *key = object;
	time_t *limit = iterator_data;
	return key_is_dead(key, *limit);
}

/*
 * Garbage collect pointers from a keyring.
 *
 * Not called with any locks held.  The keyring's key struct will not be
 * deallocated under us as only our caller may deallocate it.
 */
static void key_gc_keyring(struct key *keyring, time_t limit)
{
	int result;

	kenter("%x{%s}", keyring->serial, keyring->description ?: "");

	if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
			      (1 << KEY_FLAG_REVOKED)))
		goto dont_gc;

	/* scan the keyring looking for dead keys */
	rcu_read_lock();
	result = assoc_array_iterate(&keyring->keys,
				     key_gc_keyring_func, &limit);
	rcu_read_unlock();
	if (result == true)
		goto do_gc;

dont_gc:
	kleave(" [no gc]");
	return;

do_gc:
	keyring_gc(keyring, limit);
	kleave(" [gc]");
}

/*
 * Garbage collect a list of unreferenced, detached keys
 */
static noinline void key_gc_unused_keys(struct list_head *keys)
{
	while (!list_empty(keys)) {
		struct key *key =
			list_entry(keys->next, struct key, graveyard_link);
		list_del(&key->graveyard_link);

		kdebug("- %u", key->serial);
		key_check(key);

		security_key_free(key);

		/* deal with the user's key tracking and quota */
		if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
			spin_lock(&key->user->lock);
			key->user->qnkeys--;
			key->user->qnbytes -= key->quotalen;
			spin_unlock(&key->user->lock);
		}

		atomic_dec(&key->user->nkeys);
		if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
			atomic_dec(&key->user->nikeys);

		key_user_put(key->user);

		/* now throw away the key memory */
		if (key->type->destroy)
			key->type->destroy(key);

		kfree(key->description);

#ifdef KEY_DEBUGGING
		key->magic = KEY_DEBUG_MAGIC_X;
#endif
		kmem_cache_free(key_jar, key);
	}
}

/*
 * Garbage collector for unused keys.
 *
 * This is done in process context so that we don't have to disable interrupts
 * all over the place.  key_put() schedules this rather than trying to do the
 * cleanup itself, which means key_put() doesn't have to sleep.
 */
static void key_garbage_collector(struct work_struct *work)
{
	static LIST_HEAD(graveyard);
	static u8 gc_state;		/* Internal persistent state */
#define KEY_GC_REAP_AGAIN	0x01	/* - Need another cycle */
#define KEY_GC_REAPING_LINKS	0x02	/* - We need to reap links */
#define KEY_GC_SET_TIMER	0x04	/* - We need to restart the timer */
#define KEY_GC_REAPING_DEAD_1	0x10	/* - We need to mark dead keys */
#define KEY_GC_REAPING_DEAD_2	0x20	/* - We need to reap dead key links */
#define KEY_GC_REAPING_DEAD_3	0x40	/* - We need to reap dead keys */
#define KEY_GC_FOUND_DEAD_KEY	0x80	/* - We found at least one dead key */

	struct rb_node *cursor;
	struct key *key;
	time_t new_timer, limit;

	kenter("[%lx,%x]", key_gc_flags, gc_state);

	limit = current_kernel_time().tv_sec;
	if (limit > key_gc_delay)
		limit -= key_gc_delay;
	else
		limit = key_gc_delay;

	/* Work out what we're going to be doing in this pass */
	gc_state &= KEY_GC_REAPING_DEAD_1 | KEY_GC_REAPING_DEAD_2;
	gc_state <<= 1;
	if (test_and_clear_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags))
		gc_state |= KEY_GC_REAPING_LINKS | KEY_GC_SET_TIMER;

	if (test_and_clear_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags))
		gc_state |= KEY_GC_REAPING_DEAD_1;
	kdebug("new pass %x", gc_state);

	new_timer = LONG_MAX;

	/* As only this function is permitted to remove things from the key
	 * serial tree, if cursor is non-NULL then it will always point to a
	 * valid node in the tree - even if lock got dropped.
	 */
	spin_lock(&key_serial_lock);
	cursor = rb_first(&key_serial_tree);

continue_scanning:
	while (cursor) {
		key = rb_entry(cursor, struct key, serial_node);
		cursor = rb_next(cursor);

		if (atomic_read(&key->usage) == 0)
			goto found_unreferenced_key;

		if (unlikely(gc_state & KEY_GC_REAPING_DEAD_1)) {
			if (key->type == key_gc_dead_keytype) {
				gc_state |= KEY_GC_FOUND_DEAD_KEY;
				set_bit(KEY_FLAG_DEAD, &key->flags);
				key->perm = 0;
				goto skip_dead_key;
			}
		}

		if (gc_state & KEY_GC_SET_TIMER) {
			if (key->expiry > limit && key->expiry < new_timer) {
				kdebug("will expire %x in %ld",
				       key_serial(key), key->expiry - limit);
				new_timer = key->expiry;
			}
		}

		if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2))
			if (key->type == key_gc_dead_keytype)
				gc_state |= KEY_GC_FOUND_DEAD_KEY;

		if ((gc_state & KEY_GC_REAPING_LINKS) ||
		    unlikely(gc_state & KEY_GC_REAPING_DEAD_2)) {
			if (key->type == &key_type_keyring)
				goto found_keyring;
		}

		if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3))
			if (key->type == key_gc_dead_keytype)
				goto destroy_dead_key;

	skip_dead_key:
		if (spin_is_contended(&key_serial_lock) || need_resched())
			goto contended;
	}

contended:
	spin_unlock(&key_serial_lock);

maybe_resched:
	if (cursor) {
		cond_resched();
		spin_lock(&key_serial_lock);
		goto continue_scanning;
	}

	/* We've completed the pass.  Set the timer if we need to and queue a
	 * new cycle if necessary.  We keep executing cycles until we find one
	 * where we didn't reap any keys.
	 */
	kdebug("pass complete");

	if (gc_state & KEY_GC_SET_TIMER && new_timer != (time_t)LONG_MAX) {
		new_timer += key_gc_delay;
		key_schedule_gc(new_timer);
	}

	if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2) ||
	    !list_empty(&graveyard)) {
		/* Make sure that all pending keyring payload destructions are
		 * fulfilled and that people aren't now looking at dead or
		 * dying keys that they don't have a reference upon or a link
		 * to.
		 */
		kdebug("gc sync");
		synchronize_rcu();
	}

	if (!list_empty(&graveyard)) {
		kdebug("gc keys");
		key_gc_unused_keys(&graveyard);
	}

	if (unlikely(gc_state & (KEY_GC_REAPING_DEAD_1 |
				 KEY_GC_REAPING_DEAD_2))) {
		if (!(gc_state & KEY_GC_FOUND_DEAD_KEY)) {
			/* No remaining dead keys: short circuit the remaining
			 * keytype reap cycles.
			 */
			kdebug("dead short");
			gc_state &= ~(KEY_GC_REAPING_DEAD_1 | KEY_GC_REAPING_DEAD_2);
			gc_state |= KEY_GC_REAPING_DEAD_3;
		} else {
			gc_state |= KEY_GC_REAP_AGAIN;
		}
	}

	if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) {
		kdebug("dead wake");
		smp_mb();
		clear_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags);
		wake_up_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE);
	}

	if (gc_state & KEY_GC_REAP_AGAIN)
		schedule_work(&key_gc_work);
	kleave(" [end %x]", gc_state);
	return;

	/* We found an unreferenced key - once we've removed it from the tree,
	 * we can safely drop the lock.
	 */
found_unreferenced_key:
	kdebug("unrefd key %d", key->serial);
	rb_erase(&key->serial_node, &key_serial_tree);
	spin_unlock(&key_serial_lock);

	list_add_tail(&key->graveyard_link, &graveyard);
	gc_state |= KEY_GC_REAP_AGAIN;
	goto maybe_resched;

	/* We found a keyring and we need to check the payload for links to
	 * dead or expired keys.  We don't flag another reap immediately as we
	 * have to wait for the old payload to be destroyed by RCU before we
	 * can reap the keys to which it refers.
	 */
found_keyring:
	spin_unlock(&key_serial_lock);
	key_gc_keyring(key, limit);
	goto maybe_resched;

	/* We found a dead key that is still referenced.  Reset its type and
	 * destroy its payload with its semaphore held.
	 */
destroy_dead_key:
	spin_unlock(&key_serial_lock);
	kdebug("destroy key %d", key->serial);
	down_write(&key->sem);
	key->type = &key_type_dead;
	if (key_gc_dead_keytype->destroy)
		key_gc_dead_keytype->destroy(key);
	memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
	up_write(&key->sem);
	goto maybe_resched;
}
Commit	Line	Data
5d135440 DH	1	/* Key garbage collector
5d135440 DH	2	*
0c061b57	3	* Copyright (C) 2009-2011 Red Hat, Inc. All Rights Reserved.
5d135440 DH	4	* Written by David Howells (dhowells@redhat.com)
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public Licence
	8	* as published by the Free Software Foundation; either version
	9	* 2 of the Licence, or (at your option) any later version.
	10	*/
	11
	12	#include <linux/module.h>
8bc16dea DH	13	#include <linux/slab.h>
8bc16dea DH	14	#include <linux/security.h>
5d135440 DH	15	#include <keys/keyring-type.h>
	16	#include "internal.h"
	17
	18	/*
	19	* Delay between key revocation/expiry in seconds
	20	*/
	21	unsigned key_gc_delay = 5 * 60;
	22
	23	/*
8bc16dea DH	24	* Reaper for unused keys.
8bc16dea DH	25	*/
0c061b57 DH	26	static void key_garbage_collector(struct work_struct *work);
0c061b57 DH	27	DECLARE_WORK(key_gc_work, key_garbage_collector);
8bc16dea DH	28
	29	/*
	30	* Reaper for links from keyrings to dead keys.
5d135440 DH	31	*/
5d135440 DH	32	static void key_gc_timer_func(unsigned long);
5d135440	33	static DEFINE_TIMER(key_gc_timer, key_gc_timer_func, 0, 0);
0c061b57	34
5d135440	35	static time_t key_gc_next_run = LONG_MAX;
0c061b57 DH	36	static struct key_type *key_gc_dead_keytype;
	37
	38	static unsigned long key_gc_flags;
	39	#define KEY_GC_KEY_EXPIRED 0 /* A key expired and needs unlinking */
	40	#define KEY_GC_REAP_KEYTYPE 1 /* A keytype is being unregistered */
	41	#define KEY_GC_REAPING_KEYTYPE 2 /* Cleared when keytype reaped */
	42
	43
	44	/*
	45	* Any key whose type gets unregistered will be re-typed to this if it can't be
	46	* immediately unlinked.
	47	*/
	48	struct key_type key_type_dead = {
	49	.name = "dead",
	50	};
5d135440 DH	51
5d135440 DH	52	/*
973c9f4f DH	53	* Schedule a garbage collection run.
973c9f4f DH	54	* - time precision isn't particularly important
5d135440 DH	55	*/
	56	void key_schedule_gc(time_t gc_at)
	57	{
	58	unsigned long expires;
	59	time_t now = current_kernel_time().tv_sec;
	60
	61	kenter("%ld", gc_at - now);
	62
0c061b57 DH	63	if (gc_at <= now \|\| test_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags)) {
0c061b57 DH	64	kdebug("IMMEDIATE");
3b07e9ca	65	schedule_work(&key_gc_work);
5d135440	66	} else if (gc_at < key_gc_next_run) {
0c061b57 DH	67	kdebug("DEFERRED");
0c061b57 DH	68	key_gc_next_run = gc_at;
5d135440 DH	69	expires = jiffies + (gc_at - now) * HZ;
	70	mod_timer(&key_gc_timer, expires);
	71	}
	72	}
	73
fd75815f DH	74	/*
	75	* Schedule a dead links collection run.
	76	*/
	77	void key_schedule_gc_links(void)
	78	{
	79	set_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags);
3b07e9ca	80	schedule_work(&key_gc_work);
fd75815f DH	81	}
fd75815f DH	82
5d135440	83	/*
0c061b57 DH	84	* Some key's cleanup time was met after it expired, so we need to get the
0c061b57 DH	85	* reaper to go through a cycle finding expired keys.
5d135440 DH	86	*/
	87	static void key_gc_timer_func(unsigned long data)
	88	{
	89	kenter("");
	90	key_gc_next_run = LONG_MAX;
fd75815f	91	key_schedule_gc_links();
5d135440 DH	92	}
5d135440 DH	93
0c061b57 DH	94	/*
	95	* wait_on_bit() sleep function for uninterruptible waiting
	96	*/
	97	static int key_gc_wait_bit(void *flags)
	98	{
	99	schedule();
	100	return 0;
	101	}
	102
	103	/*
	104	* Reap keys of dead type.
	105	*
	106	* We use three flags to make sure we see three complete cycles of the garbage
	107	* collector: the first to mark keys of that type as being dead, the second to
	108	* collect dead links and the third to clean up the dead keys. We have to be
	109	* careful as there may already be a cycle in progress.
	110	*
	111	* The caller must be holding key_types_sem.
	112	*/
	113	void key_gc_keytype(struct key_type *ktype)
	114	{
	115	kenter("%s", ktype->name);
	116
	117	key_gc_dead_keytype = ktype;
	118	set_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags);
	119	smp_mb();
	120	set_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags);
	121
	122	kdebug("schedule");
3b07e9ca	123	schedule_work(&key_gc_work);
0c061b57 DH	124
	125	kdebug("sleep");
	126	wait_on_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE, key_gc_wait_bit,
	127	TASK_UNINTERRUPTIBLE);
	128
	129	key_gc_dead_keytype = NULL;
	130	kleave("");
	131	}
	132
b2a4df20 DH	133	static int key_gc_keyring_func(const void object, void iterator_data)
	134	{
	135	const struct key *key = object;
	136	time_t *limit = iterator_data;
	137	return key_is_dead(key, *limit);
	138	}
	139
5d135440	140	/*
973c9f4f DH	141	* Garbage collect pointers from a keyring.
973c9f4f DH	142	*
0c061b57 DH	143	* Not called with any locks held. The keyring's key struct will not be
0c061b57 DH	144	* deallocated under us as only our caller may deallocate it.
5d135440	145	*/
0c061b57	146	static void key_gc_keyring(struct key *keyring, time_t limit)
5d135440	147	{
b2a4df20	148	int result;
5d135440	149
b2a4df20	150	kenter("%x{%s}", keyring->serial, keyring->description ?: "");
5d135440	151
fd75815f DH	152	if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) \|
fd75815f DH	153	(1 << KEY_FLAG_REVOKED)))
5d135440 DH	154	goto dont_gc;
	155
	156	/* scan the keyring looking for dead keys */
cf8304e8	157	rcu_read_lock();
b2a4df20 DH	158	result = assoc_array_iterate(&keyring->keys,
b2a4df20 DH	159	key_gc_keyring_func, &limit);
cf8304e8	160	rcu_read_unlock();
b2a4df20 DH	161	if (result == true)
	162	goto do_gc;
	163
5d135440	164	dont_gc:
0c061b57 DH	165	kleave(" [no gc]");
0c061b57 DH	166	return;
5d135440 DH	167
5d135440 DH	168	do_gc:
5d135440	169	keyring_gc(keyring, limit);
0c061b57	170	kleave(" [gc]");
5d135440 DH	171	}
	172
	173	/*
65d87fe6	174	* Garbage collect a list of unreferenced, detached keys
5d135440	175	*/
65d87fe6	176	static noinline void key_gc_unused_keys(struct list_head *keys)
5d135440	177	{
65d87fe6 DH	178	while (!list_empty(keys)) {
	179	struct key *key =
	180	list_entry(keys->next, struct key, graveyard_link);
	181	list_del(&key->graveyard_link);
	182
	183	kdebug("- %u", key->serial);
	184	key_check(key);
	185
	186	security_key_free(key);
	187
	188	/* deal with the user's key tracking and quota */
	189	if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
	190	spin_lock(&key->user->lock);
	191	key->user->qnkeys--;
	192	key->user->qnbytes -= key->quotalen;
	193	spin_unlock(&key->user->lock);
	194	}
5d135440	195
65d87fe6 DH	196	atomic_dec(&key->user->nkeys);
	197	if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
	198	atomic_dec(&key->user->nikeys);
5d135440	199
65d87fe6	200	key_user_put(key->user);
5d135440	201
65d87fe6 DH	202	/* now throw away the key memory */
	203	if (key->type->destroy)
	204	key->type->destroy(key);
5d135440	205
65d87fe6	206	kfree(key->description);
5d135440	207
0c061b57	208	#ifdef KEY_DEBUGGING
65d87fe6	209	key->magic = KEY_DEBUG_MAGIC_X;
0c061b57	210	#endif
65d87fe6 DH	211	kmem_cache_free(key_jar, key);
65d87fe6 DH	212	}
5d135440	213	}
8bc16dea DH	214
	215	/*
	216	* Garbage collector for unused keys.
	217	*
	218	* This is done in process context so that we don't have to disable interrupts
	219	* all over the place. key_put() schedules this rather than trying to do the
	220	* cleanup itself, which means key_put() doesn't have to sleep.
	221	*/
0c061b57	222	static void key_garbage_collector(struct work_struct *work)
8bc16dea	223	{
65d87fe6	224	static LIST_HEAD(graveyard);
0c061b57 DH	225	static u8 gc_state; /* Internal persistent state */
	226	#define KEY_GC_REAP_AGAIN 0x01 /* - Need another cycle */
	227	#define KEY_GC_REAPING_LINKS 0x02 /* - We need to reap links */
	228	#define KEY_GC_SET_TIMER 0x04 /* - We need to restart the timer */
	229	#define KEY_GC_REAPING_DEAD_1 0x10 /* - We need to mark dead keys */
	230	#define KEY_GC_REAPING_DEAD_2 0x20 /* - We need to reap dead key links */
	231	#define KEY_GC_REAPING_DEAD_3 0x40 /* - We need to reap dead keys */
	232	#define KEY_GC_FOUND_DEAD_KEY 0x80 /* - We found at least one dead key */
	233
	234	struct rb_node *cursor;
8bc16dea	235	struct key *key;
0c061b57 DH	236	time_t new_timer, limit;
	237
	238	kenter("[%lx,%x]", key_gc_flags, gc_state);
	239
	240	limit = current_kernel_time().tv_sec;
	241	if (limit > key_gc_delay)
	242	limit -= key_gc_delay;
	243	else
	244	limit = key_gc_delay;
	245
	246	/* Work out what we're going to be doing in this pass */
	247	gc_state &= KEY_GC_REAPING_DEAD_1 \| KEY_GC_REAPING_DEAD_2;
	248	gc_state <<= 1;
	249	if (test_and_clear_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags))
	250	gc_state \|= KEY_GC_REAPING_LINKS \| KEY_GC_SET_TIMER;
	251
	252	if (test_and_clear_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags))
	253	gc_state \|= KEY_GC_REAPING_DEAD_1;
	254	kdebug("new pass %x", gc_state);
	255
	256	new_timer = LONG_MAX;
8bc16dea	257
0c061b57 DH	258	/* As only this function is permitted to remove things from the key
	259	* serial tree, if cursor is non-NULL then it will always point to a
	260	* valid node in the tree - even if lock got dropped.
	261	*/
8bc16dea	262	spin_lock(&key_serial_lock);
0c061b57	263	cursor = rb_first(&key_serial_tree);
8bc16dea	264
0c061b57 DH	265	continue_scanning:
	266	while (cursor) {
	267	key = rb_entry(cursor, struct key, serial_node);
	268	cursor = rb_next(cursor);
8bc16dea DH	269
8bc16dea DH	270	if (atomic_read(&key->usage) == 0)
0c061b57 DH	271	goto found_unreferenced_key;
	272
	273	if (unlikely(gc_state & KEY_GC_REAPING_DEAD_1)) {
	274	if (key->type == key_gc_dead_keytype) {
	275	gc_state \|= KEY_GC_FOUND_DEAD_KEY;
	276	set_bit(KEY_FLAG_DEAD, &key->flags);
	277	key->perm = 0;
	278	goto skip_dead_key;
	279	}
	280	}
	281
	282	if (gc_state & KEY_GC_SET_TIMER) {
	283	if (key->expiry > limit && key->expiry < new_timer) {
	284	kdebug("will expire %x in %ld",
	285	key_serial(key), key->expiry - limit);
	286	new_timer = key->expiry;
	287	}
	288	}
	289
	290	if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2))
	291	if (key->type == key_gc_dead_keytype)
	292	gc_state \|= KEY_GC_FOUND_DEAD_KEY;
	293
	294	if ((gc_state & KEY_GC_REAPING_LINKS) \|\|
	295	unlikely(gc_state & KEY_GC_REAPING_DEAD_2)) {
	296	if (key->type == &key_type_keyring)
	297	goto found_keyring;
	298	}
	299
	300	if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3))
	301	if (key->type == key_gc_dead_keytype)
	302	goto destroy_dead_key;
	303
	304	skip_dead_key:
	305	if (spin_is_contended(&key_serial_lock) \|\| need_resched())
	306	goto contended;
8bc16dea DH	307	}
8bc16dea DH	308
0c061b57	309	contended:
8bc16dea	310	spin_unlock(&key_serial_lock);
8bc16dea	311
0c061b57 DH	312	maybe_resched:
	313	if (cursor) {
	314	cond_resched();
	315	spin_lock(&key_serial_lock);
	316	goto continue_scanning;
	317	}
8bc16dea	318
0c061b57 DH	319	/* We've completed the pass. Set the timer if we need to and queue a
	320	* new cycle if necessary. We keep executing cycles until we find one
	321	* where we didn't reap any keys.
	322	*/
	323	kdebug("pass complete");
8bc16dea	324
0c061b57 DH	325	if (gc_state & KEY_GC_SET_TIMER && new_timer != (time_t)LONG_MAX) {
	326	new_timer += key_gc_delay;
	327	key_schedule_gc(new_timer);
	328	}
8bc16dea	329
65d87fe6 DH	330	if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2) \|\|
	331	!list_empty(&graveyard)) {
	332	/* Make sure that all pending keyring payload destructions are
	333	* fulfilled and that people aren't now looking at dead or
	334	* dying keys that they don't have a reference upon or a link
	335	* to.
0c061b57	336	*/
65d87fe6	337	kdebug("gc sync");
0c061b57	338	synchronize_rcu();
8bc16dea DH	339	}
8bc16dea DH	340
65d87fe6 DH	341	if (!list_empty(&graveyard)) {
	342	kdebug("gc keys");
	343	key_gc_unused_keys(&graveyard);
	344	}
	345
0c061b57 DH	346	if (unlikely(gc_state & (KEY_GC_REAPING_DEAD_1 \|
	347	KEY_GC_REAPING_DEAD_2))) {
	348	if (!(gc_state & KEY_GC_FOUND_DEAD_KEY)) {
	349	/* No remaining dead keys: short circuit the remaining
	350	* keytype reap cycles.
	351	*/
	352	kdebug("dead short");
	353	gc_state &= ~(KEY_GC_REAPING_DEAD_1 \| KEY_GC_REAPING_DEAD_2);
	354	gc_state \|= KEY_GC_REAPING_DEAD_3;
	355	} else {
	356	gc_state \|= KEY_GC_REAP_AGAIN;
	357	}
	358	}
8bc16dea	359
0c061b57 DH	360	if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) {
	361	kdebug("dead wake");
	362	smp_mb();
	363	clear_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags);
	364	wake_up_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE);
	365	}
8bc16dea	366
0c061b57	367	if (gc_state & KEY_GC_REAP_AGAIN)
3b07e9ca	368	schedule_work(&key_gc_work);
0c061b57 DH	369	kleave(" [end %x]", gc_state);
0c061b57 DH	370	return;
8bc16dea	371
0c061b57 DH	372	/* We found an unreferenced key - once we've removed it from the tree,
	373	* we can safely drop the lock.
	374	*/
	375	found_unreferenced_key:
	376	kdebug("unrefd key %d", key->serial);
	377	rb_erase(&key->serial_node, &key_serial_tree);
	378	spin_unlock(&key_serial_lock);
8bc16dea	379
65d87fe6	380	list_add_tail(&key->graveyard_link, &graveyard);
0c061b57 DH	381	gc_state \|= KEY_GC_REAP_AGAIN;
0c061b57 DH	382	goto maybe_resched;
8bc16dea	383
0c061b57 DH	384	/* We found a keyring and we need to check the payload for links to
	385	* dead or expired keys. We don't flag another reap immediately as we
	386	* have to wait for the old payload to be destroyed by RCU before we
	387	* can reap the keys to which it refers.
	388	*/
	389	found_keyring:
	390	spin_unlock(&key_serial_lock);
0c061b57 DH	391	key_gc_keyring(key, limit);
	392	goto maybe_resched;
	393
	394	/* We found a dead key that is still referenced. Reset its type and
	395	* destroy its payload with its semaphore held.
	396	*/
	397	destroy_dead_key:
	398	spin_unlock(&key_serial_lock);
	399	kdebug("destroy key %d", key->serial);
	400	down_write(&key->sem);
	401	key->type = &key_type_dead;
	402	if (key_gc_dead_keytype->destroy)
	403	key_gc_dead_keytype->destroy(key);
	404	memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
	405	up_write(&key->sem);
	406	goto maybe_resched;
8bc16dea	407	}