diff options
Diffstat (limited to 'security/keys/gc.c')
| -rw-r--r-- | security/keys/gc.c | 222 |
1 files changed, 222 insertions, 0 deletions
diff --git a/security/keys/gc.c b/security/keys/gc.c new file mode 100644 index 00000000..89df6b5f --- /dev/null +++ b/security/keys/gc.c @@ -0,0 +1,222 @@ +/* Key garbage collector + * + * Copyright (C) 2009 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 <keys/keyring-type.h> +#include "internal.h" + +/* + * Delay between key revocation/expiry in seconds + */ +unsigned key_gc_delay = 5 * 60; + +/* + * Reaper + */ +static void key_gc_timer_func(unsigned long); +static void key_garbage_collector(struct work_struct *); +static DEFINE_TIMER(key_gc_timer, key_gc_timer_func, 0, 0); +static DECLARE_WORK(key_gc_work, key_garbage_collector); +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; + +/* + * 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) { + schedule_work(&key_gc_work); + } else if (gc_at < key_gc_next_run) { + expires = jiffies + (gc_at - now) * HZ; + mod_timer(&key_gc_timer, expires); + } +} + +/* + * The garbage collector timer kicked off + */ +static void key_gc_timer_func(unsigned long data) +{ + kenter(""); + key_gc_next_run = LONG_MAX; + schedule_work(&key_gc_work); +} + +/* + * Garbage collect pointers from a keyring. + * + * Return true if we altered the keyring. + */ +static bool key_gc_keyring(struct key *keyring, time_t limit) + __releases(key_serial_lock) +{ + 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; + + for (loop = klist->nkeys - 1; 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(" = false"); + return false; + +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; +} + +/* + * Garbage collector for keys. This involves scanning the keyrings for dead, + * expired and revoked keys that have overstayed their welcome + */ +static void key_garbage_collector(struct work_struct *work) +{ + 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); + + if (unlikely(RB_EMPTY_ROOT(&key_serial_tree))) { + spin_unlock(&key_serial_lock); + clear_bit(0, &key_gc_executing); + return; + } + + 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; + } + } + + 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; + } + + 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; + + rb = rb_next(&key->serial_node); + if (!rb) + goto reached_the_end; + key = rb_entry(rb, struct key, serial_node); + } + +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); + schedule_work(&key_gc_work); + kleave(" [continue]"); + return; + + /* 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]"); +} |