/*
* 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)
{
struct keyring_list *klist;
struct key *key;
int loop;
kenter("%x", key_serial(keyring));
if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
goto dont_gc;
/* scan the keyring looking for dead keys */
rcu_read_lock();
klist = rcu_dereference(keyring->payload.subscriptions);
if (!klist)
goto unlock_dont_gc;
loop = klist->nkeys;
smp_rmb();
for (loop--; loop >= 0; loop--) {
key = klist->keys[loop];
if (test_bit(KEY_FLAG_DEAD, &key->flags) ||
(key->expiry > 0 && key->expiry <= limit))
goto do_gc;
}
unlock_dont_gc:
rcu_read_unlock();
dont_gc:
kleave(" [no gc]");
return;
do_gc:
rcu_read_unlock();
keyring_gc(keyring, limit);
kleave(" [gc]");
}
/*
* 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)
{
struct keyring_list *klist;
int loop;
kenter("%x", key_serial(keyring));
if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
(1 << KEY_FLAG_REVOKED)))
goto dont_gc;
/* scan the keyring looking for dead keys */
rcu_read_lock();
klist = rcu_dereference(keyring->payload.subscriptions);
if (!klist)
goto unlock_dont_gc;
loop = klist->nkeys;
smp_rmb();
for (loop--; loop >= 0; loop--) {
struct key *key = rcu_dereference(klist->keys[loop]);
if (key_is_dead(key, limit))
goto do_gc;
}
unlock_dont_gc:
rcu_read_unlock();
dont_gc:
kleave(" [no gc]");
return;
do_gc:
rcu_read_unlock();
keyring_gc(keyring, limit);
kleave(" [gc]");
}
/*
* 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);
keyring_gc(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;
}