From 272e77de798362c31e6452a46a0e7d5b6aaeb550 Mon Sep 17 00:00:00 2001 From: Wolfgang Wiedmeyer Date: Fri, 23 Oct 2015 23:15:19 +0200 Subject: first round of updates to the security code --- security/keys/gc.c | 386 ++++++++++++++++++++++++++++++++++++++--------------- 1 file changed, 276 insertions(+), 110 deletions(-) (limited to 'security/keys/gc.c') diff --git a/security/keys/gc.c b/security/keys/gc.c index 89df6b5..2e2395d 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 @@ -10,6 +10,8 @@ */ #include +#include +#include #include #include "internal.h" @@ -19,17 +21,33 @@ unsigned key_gc_delay = 5 * 60; /* - * Reaper + * Reaper for 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_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; +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. @@ -42,31 +60,75 @@ void key_schedule_gc(time_t gc_at) kenter("%ld", gc_at - now); - if (gc_at <= now) { - schedule_work(&key_gc_work); + 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; - schedule_work(&key_gc_work); + 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; @@ -93,130 +155,234 @@ 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 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_garbage_collector(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; + key_check(key); + + security_key_free(key); + + /* 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); } - limit = now; + atomic_dec(&key->user->nkeys); + if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) + atomic_dec(&key->user->nikeys); + + /* now throw away the key memory */ + if (key->type->destroy) + key->type->destroy(key); + + key_user_put(key->user); + + kfree(key->description); + +#ifdef KEY_DEBUGGING + key->magic = KEY_DEBUG_MAGIC_X; +#endif + kmem_cache_free(key_jar, key); +} + +/* + * 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 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); - if (unlikely(RB_EMPTY_ROOT(&key_serial_tree))) { - spin_unlock(&key_serial_lock); - clear_bit(0, &key_gc_executing); - return; - } +continue_scanning: + while (cursor) { + key = rb_entry(cursor, struct key, serial_node); + cursor = rb_next(cursor); - 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 (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 (!key) - goto reached_the_end; + if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2)) + if (key->type == key_gc_dead_keytype) + gc_state |= KEY_GC_FOUND_DEAD_KEY; - /* 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 ((gc_state & KEY_GC_REAPING_LINKS) || + unlikely(gc_state & KEY_GC_REAPING_DEAD_2)) { + if (key->type == &key_type_keyring) + goto found_keyring; } - 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; + if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) + if (key->type == key_gc_dead_keytype) + goto destroy_dead_key; - rb = rb_next(&key->serial_node); - if (!rb) - goto reached_the_end; - key = rb_entry(rb, struct key, serial_node); + skip_dead_key: + if (spin_is_contended(&key_serial_lock) || need_resched()) + goto contended; } -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"); +contended: 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) { + +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); } - kleave(" [end]"); + + 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(); + } + + 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) + queue_work(system_nrt_wq, &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); + + key_gc_unused_key(key); + 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); + 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; } -- cgit v1.1