diff options
Diffstat (limited to 'security/keys/gc.c')
| -rw-r--r-- | security/keys/gc.c | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/security/keys/gc.c b/security/keys/gc.c new file mode 100644 index 000000000000..1e616aef55fd --- /dev/null +++ b/security/keys/gc.c @@ -0,0 +1,194 @@ +/* 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 unsigned long key_gc_executing; +static time_t key_gc_next_run = LONG_MAX; + +/* + * Schedule a garbage collection run + * - 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); + + gc_at += key_gc_delay; + + if (now >= gc_at) { + 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 */ + klist = rcu_dereference(keyring->payload.subscriptions); + if (!klist) + goto 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; + } + +dont_gc: + kleave(" = false"); + return false; + +do_gc: + 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; + + kenter(""); + + if (test_and_set_bit(0, &key_gc_executing)) { + key_schedule_gc(current_kernel_time().tv_sec); + return; + } + + limit = current_kernel_time().tv_sec; + if (limit > key_gc_delay) + limit -= key_gc_delay; + else + limit = key_gc_delay; + + spin_lock(&key_serial_lock); + + if (RB_EMPTY_ROOT(&key_serial_tree)) + goto reached_the_end; + + cursor = key_gc_cursor; + if (cursor < 0) + cursor = 0; + + /* 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 > 0 && key->expiry < new_timer) + new_timer = key->expiry; + + if (key->type == &key_type_keyring && + key_gc_keyring(key, limit)) { + /* the gc ate our lock */ + schedule_work(&key_gc_work); + goto no_unlock; + } + + rb = rb_next(&key->serial_node); + if (!rb) { + key_gc_cursor = 0; + break; + } + key = rb_entry(rb, struct key, serial_node); + } + +out: + spin_unlock(&key_serial_lock); +no_unlock: + clear_bit(0, &key_gc_executing); + if (new_timer < LONG_MAX) + key_schedule_gc(new_timer); + + kleave(""); + return; + +reached_the_end: + key_gc_cursor = 0; + goto out; +} |