diff options
| -rw-r--r-- | security/keys/gc.c | 411 | ||||
| -rw-r--r-- | security/keys/internal.h | 4 | ||||
| -rw-r--r-- | security/keys/key.c | 51 |
3 files changed, 258 insertions, 208 deletions
diff --git a/security/keys/gc.c b/security/keys/gc.c index d67e88b..bf4d8da 100644 --- a/security/keys/gc.c +++ b/security/keys/gc.c @@ -1,6 +1,6 @@ /* 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 @@ -23,21 +23,31 @@ unsigned key_gc_delay = 5 * 60; /* * 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. @@ -50,31 +60,75 @@ void key_schedule_gc(time_t gc_at) 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; @@ -101,134 +155,49 @@ static bool key_gc_keyring(struct key *keyring, time_t limit) 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); } /* @@ -238,60 +207,182 @@ reached_the_end: * 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; } diff --git a/security/keys/internal.h b/security/keys/internal.h index a7cd1a6..c7a7cae 100644 --- a/security/keys/internal.h +++ b/security/keys/internal.h @@ -31,6 +31,7 @@ no_printk(KERN_DEBUG FMT"\n", ##__VA_ARGS__) #endif +extern struct key_type key_type_dead; extern struct key_type key_type_user; /*****************************************************************************/ @@ -147,10 +148,11 @@ extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags, extern long join_session_keyring(const char *name); -extern struct work_struct key_gc_unused_work; +extern struct work_struct key_gc_work; extern unsigned key_gc_delay; extern void keyring_gc(struct key *keyring, time_t limit); extern void key_schedule_gc(time_t expiry_at); +extern void key_gc_keytype(struct key_type *ktype); extern int key_task_permission(const key_ref_t key_ref, const struct cred *cred, diff --git a/security/keys/key.c b/security/keys/key.c index 1f3ed44..4414abd 100644 --- a/security/keys/key.c +++ b/security/keys/key.c @@ -39,11 +39,6 @@ static DECLARE_RWSEM(key_types_sem); /* We serialise key instantiation and link */ DEFINE_MUTEX(key_construction_mutex); -/* Any key who's type gets unegistered will be re-typed to this */ -static struct key_type key_type_dead = { - .name = "dead", -}; - #ifdef KEY_DEBUGGING void __key_check(const struct key *key) { @@ -602,7 +597,7 @@ void key_put(struct key *key) key_check(key); if (atomic_dec_and_test(&key->usage)) - queue_work(system_nrt_wq, &key_gc_unused_work); + queue_work(system_nrt_wq, &key_gc_work); } } EXPORT_SYMBOL(key_put); @@ -980,49 +975,11 @@ EXPORT_SYMBOL(register_key_type); */ void unregister_key_type(struct key_type *ktype) { - struct rb_node *_n; - struct key *key; - down_write(&key_types_sem); - - /* withdraw the key type */ list_del_init(&ktype->link); - - /* mark all the keys of this type dead */ - spin_lock(&key_serial_lock); - - for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) { - key = rb_entry(_n, struct key, serial_node); - - if (key->type == ktype) { - key->type = &key_type_dead; - set_bit(KEY_FLAG_DEAD, &key->flags); - } - } - - spin_unlock(&key_serial_lock); - - /* make sure everyone revalidates their keys */ - synchronize_rcu(); - - /* we should now be able to destroy the payloads of all the keys of - * this type with impunity */ - spin_lock(&key_serial_lock); - - for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) { - key = rb_entry(_n, struct key, serial_node); - - if (key->type == ktype) { - if (ktype->destroy) - ktype->destroy(key); - memset(&key->payload, KEY_DESTROY, sizeof(key->payload)); - } - } - - spin_unlock(&key_serial_lock); - up_write(&key_types_sem); - - key_schedule_gc(0); + downgrade_write(&key_types_sem); + key_gc_keytype(ktype); + up_read(&key_types_sem); } EXPORT_SYMBOL(unregister_key_type); |
