/* Key garbage collector
*
- * Copyright (C) 2009 Red Hat, Inc. All Rights Reserved.
+ * 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
/*
* Reaper for unused keys.
*/
-static void key_gc_unused_keys(struct work_struct *work);
-DECLARE_WORK(key_gc_unused_work, key_gc_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 void key_gc_dead_links(struct work_struct *);
static DEFINE_TIMER(key_gc_timer, key_gc_timer_func, 0, 0);
-static DECLARE_WORK(key_gc_work, key_gc_dead_links);
-static key_serial_t key_gc_cursor; /* the last key the gc considered */
-static bool key_gc_again;
-static unsigned long key_gc_executing;
+
static time_t key_gc_next_run = LONG_MAX;
-static time_t key_gc_new_timer;
+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.
kenter("%ld", gc_at - now);
- if (gc_at <= now) {
+ if (gc_at <= now || test_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags)) {
+ kdebug("IMMEDIATE");
queue_work(system_nrt_wq, &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);
}
}
/*
- * The garbage collector timer kicked off
+ * 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;
+ set_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags);
queue_work(system_nrt_wq, &key_gc_work);
}
+/*
+ * 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");
+ queue_work(system_nrt_wq, &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("");
+}
+
/*
* Garbage collect pointers from a keyring.
*
- * Return true if we altered the 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 bool key_gc_keyring(struct key *keyring, time_t limit)
- __releases(key_serial_lock)
+static void key_gc_keyring(struct key *keyring, time_t limit)
{
struct keyring_list *klist;
struct key *key;
unlock_dont_gc:
rcu_read_unlock();
dont_gc:
- kleave(" = false");
- return false;
+ kleave(" [no gc]");
+ return;
do_gc:
rcu_read_unlock();
- key_gc_cursor = keyring->serial;
- key_get(keyring);
- spin_unlock(&key_serial_lock);
+
keyring_gc(keyring, limit);
- key_put(keyring);
- kleave(" = true");
- return true;
+ kleave(" [gc]");
}
/*
- * Garbage collector for links to dead keys.
- *
- * This involves scanning the keyrings for dead, expired and revoked keys that
- * have overstayed their welcome
+ * Garbage collect an unreferenced, detached key
*/
-static void key_gc_dead_links(struct work_struct *work)
+static noinline void key_gc_unused_key(struct key *key)
{
- struct rb_node *rb;
- key_serial_t cursor;
- struct key *key, *xkey;
- time_t new_timer = LONG_MAX, limit, now;
-
- now = current_kernel_time().tv_sec;
- kenter("[%x,%ld]", key_gc_cursor, key_gc_new_timer - now);
-
- if (test_and_set_bit(0, &key_gc_executing)) {
- key_schedule_gc(current_kernel_time().tv_sec + 1);
- kleave(" [busy; deferring]");
- return;
- }
-
- limit = now;
- if (limit > key_gc_delay)
- limit -= key_gc_delay;
- else
- limit = key_gc_delay;
-
- spin_lock(&key_serial_lock);
+ key_check(key);
- if (unlikely(RB_EMPTY_ROOT(&key_serial_tree))) {
- spin_unlock(&key_serial_lock);
- clear_bit(0, &key_gc_executing);
- return;
- }
+ security_key_free(key);
- cursor = key_gc_cursor;
- if (cursor < 0)
- cursor = 0;
- if (cursor > 0)
- new_timer = key_gc_new_timer;
- else
- key_gc_again = false;
-
- /* find the first key above the cursor */
- key = NULL;
- rb = key_serial_tree.rb_node;
- while (rb) {
- xkey = rb_entry(rb, struct key, serial_node);
- if (cursor < xkey->serial) {
- key = xkey;
- rb = rb->rb_left;
- } else if (cursor > xkey->serial) {
- rb = rb->rb_right;
- } else {
- rb = rb_next(rb);
- if (!rb)
- goto reached_the_end;
- key = rb_entry(rb, struct key, serial_node);
- break;
- }
+ /* 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);
}
- if (!key)
- goto reached_the_end;
-
- /* trawl through the keys looking for keyrings */
- for (;;) {
- if (key->expiry > limit && key->expiry < new_timer) {
- kdebug("will expire %x in %ld",
- key_serial(key), key->expiry - limit);
- new_timer = key->expiry;
- }
+ atomic_dec(&key->user->nkeys);
+ if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
+ atomic_dec(&key->user->nikeys);
- if (key->type == &key_type_keyring &&
- key_gc_keyring(key, limit))
- /* the gc had to release our lock so that the keyring
- * could be modified, so we have to get it again */
- goto gc_released_our_lock;
+ key_user_put(key->user);
- rb = rb_next(&key->serial_node);
- if (!rb)
- goto reached_the_end;
- key = rb_entry(rb, struct key, serial_node);
- }
+ /* now throw away the key memory */
+ if (key->type->destroy)
+ key->type->destroy(key);
-gc_released_our_lock:
- kdebug("gc_released_our_lock");
- key_gc_new_timer = new_timer;
- key_gc_again = true;
- clear_bit(0, &key_gc_executing);
- queue_work(system_nrt_wq, &key_gc_work);
- kleave(" [continue]");
- return;
+ kfree(key->description);
- /* when we reach the end of the run, we set the timer for the next one */
-reached_the_end:
- kdebug("reached_the_end");
- spin_unlock(&key_serial_lock);
- key_gc_new_timer = new_timer;
- key_gc_cursor = 0;
- clear_bit(0, &key_gc_executing);
-
- if (key_gc_again) {
- /* there may have been a key that expired whilst we were
- * scanning, so if we discarded any links we should do another
- * scan */
- new_timer = now + 1;
- key_schedule_gc(new_timer);
- } else if (new_timer < LONG_MAX) {
- new_timer += key_gc_delay;
- key_schedule_gc(new_timer);
- }
- kleave(" [end]");
+#ifdef KEY_DEBUGGING
+ key->magic = KEY_DEBUG_MAGIC_X;
+#endif
+ kmem_cache_free(key_jar, key);
}
/*
* 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_gc_unused_keys(struct work_struct *work)
+static void key_garbage_collector(struct work_struct *work)
{
- struct rb_node *_n;
+ 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;
-go_again:
- /* look for a dead key in the tree */
+ /* 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);
- for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
- key = rb_entry(_n, struct key, serial_node);
+continue_scanning:
+ while (cursor) {
+ key = rb_entry(cursor, struct key, serial_node);
+ cursor = rb_next(cursor);
if (atomic_read(&key->usage) == 0)
- goto found_dead_key;
+ 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);
- return;
-found_dead_key:
- /* we found a dead key - once we've removed it from the tree, we can
- * drop the lock */
- rb_erase(&key->serial_node, &key_serial_tree);
- spin_unlock(&key_serial_lock);
+maybe_resched:
+ if (cursor) {
+ cond_resched();
+ spin_lock(&key_serial_lock);
+ goto continue_scanning;
+ }
- key_check(key);
+ /* 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");
- security_key_free(key);
+ if (gc_state & KEY_GC_SET_TIMER && new_timer != (time_t)LONG_MAX) {
+ new_timer += key_gc_delay;
+ key_schedule_gc(new_timer);
+ }
- /* 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);
+ if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2)) {
+ /* Make sure everyone revalidates their keys if we marked a
+ * bunch as being dead and make sure all keyring ex-payloads
+ * are destroyed.
+ */
+ kdebug("dead sync");
+ synchronize_rcu();
}
- atomic_dec(&key->user->nkeys);
- if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
- atomic_dec(&key->user->nikeys);
+ 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;
+ }
+ }
- key_user_put(key->user);
+ 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);
+ }
- /* now throw away the key memory */
- if (key->type->destroy)
- key->type->destroy(key);
+ if (gc_state & KEY_GC_REAP_AGAIN)
+ queue_work(system_nrt_wq, &key_gc_work);
+ kleave(" [end %x]", gc_state);
+ return;
- kfree(key->description);
+ /* 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);
-#ifdef KEY_DEBUGGING
- key->magic = KEY_DEBUG_MAGIC_X;
-#endif
- kmem_cache_free(key_jar, key);
+ key_gc_unused_key(key);
+ gc_state |= KEY_GC_REAP_AGAIN;
+ goto maybe_resched;
- /* there may, of course, be more than one key to destroy */
- goto go_again;
+ /* 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);
+ kdebug("scan keyring %d", key->serial);
+ 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;
}
git.openpandora.org / pandora-kernel.git / commitdiff