![Tejun Heo](/assets/img/avatar_default.png)
system_nrt[_freezable]_wq are now spurious. Mark them deprecated and convert all users to system[_freezable]_wq. If you're cc'd and wondering what's going on: Now all workqueues are non-reentrant, so there's no reason to use system_nrt[_freezable]_wq. Please use system[_freezable]_wq instead. This patch doesn't make any functional difference. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-By: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: David Airlie <airlied@linux.ie> Cc: Jiri Kosina <jkosina@suse.cz> Cc: "David S. Miller" <davem@davemloft.net> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: David Howells <dhowells@redhat.com>
413 lines
11 KiB
C
413 lines
11 KiB
C
/* Key garbage collector
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*
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* Copyright (C) 2009-2011 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/security.h>
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#include <keys/keyring-type.h>
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#include "internal.h"
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/*
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* Delay between key revocation/expiry in seconds
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*/
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unsigned key_gc_delay = 5 * 60;
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/*
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* Reaper for unused keys.
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*/
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static void key_garbage_collector(struct work_struct *work);
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DECLARE_WORK(key_gc_work, key_garbage_collector);
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/*
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* Reaper for links from keyrings to dead keys.
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*/
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static void key_gc_timer_func(unsigned long);
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static DEFINE_TIMER(key_gc_timer, key_gc_timer_func, 0, 0);
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static time_t key_gc_next_run = LONG_MAX;
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static struct key_type *key_gc_dead_keytype;
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static unsigned long key_gc_flags;
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#define KEY_GC_KEY_EXPIRED 0 /* A key expired and needs unlinking */
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#define KEY_GC_REAP_KEYTYPE 1 /* A keytype is being unregistered */
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#define KEY_GC_REAPING_KEYTYPE 2 /* Cleared when keytype reaped */
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/*
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* Any key whose type gets unregistered will be re-typed to this if it can't be
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* immediately unlinked.
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*/
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struct key_type key_type_dead = {
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.name = "dead",
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};
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/*
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* Schedule a garbage collection run.
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* - time precision isn't particularly important
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*/
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void key_schedule_gc(time_t gc_at)
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{
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unsigned long expires;
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time_t now = current_kernel_time().tv_sec;
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kenter("%ld", gc_at - now);
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if (gc_at <= now || test_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags)) {
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kdebug("IMMEDIATE");
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schedule_work(&key_gc_work);
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} else if (gc_at < key_gc_next_run) {
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kdebug("DEFERRED");
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key_gc_next_run = gc_at;
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expires = jiffies + (gc_at - now) * HZ;
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mod_timer(&key_gc_timer, expires);
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}
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}
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/*
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* Schedule a dead links collection run.
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*/
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void key_schedule_gc_links(void)
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{
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set_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags);
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schedule_work(&key_gc_work);
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}
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/*
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* Some key's cleanup time was met after it expired, so we need to get the
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* reaper to go through a cycle finding expired keys.
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*/
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static void key_gc_timer_func(unsigned long data)
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{
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kenter("");
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key_gc_next_run = LONG_MAX;
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key_schedule_gc_links();
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}
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/*
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* wait_on_bit() sleep function for uninterruptible waiting
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*/
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static int key_gc_wait_bit(void *flags)
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{
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schedule();
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return 0;
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}
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/*
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* Reap keys of dead type.
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*
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* We use three flags to make sure we see three complete cycles of the garbage
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* collector: the first to mark keys of that type as being dead, the second to
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* collect dead links and the third to clean up the dead keys. We have to be
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* careful as there may already be a cycle in progress.
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*
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* The caller must be holding key_types_sem.
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*/
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void key_gc_keytype(struct key_type *ktype)
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{
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kenter("%s", ktype->name);
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key_gc_dead_keytype = ktype;
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set_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags);
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smp_mb();
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set_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags);
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kdebug("schedule");
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schedule_work(&key_gc_work);
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kdebug("sleep");
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wait_on_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE, key_gc_wait_bit,
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TASK_UNINTERRUPTIBLE);
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key_gc_dead_keytype = NULL;
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kleave("");
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}
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/*
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* Garbage collect pointers from a keyring.
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*
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* Not called with any locks held. The keyring's key struct will not be
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* deallocated under us as only our caller may deallocate it.
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*/
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static void key_gc_keyring(struct key *keyring, time_t limit)
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{
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struct keyring_list *klist;
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int loop;
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kenter("%x", key_serial(keyring));
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if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
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(1 << KEY_FLAG_REVOKED)))
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goto dont_gc;
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/* scan the keyring looking for dead keys */
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rcu_read_lock();
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klist = rcu_dereference(keyring->payload.subscriptions);
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if (!klist)
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goto unlock_dont_gc;
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loop = klist->nkeys;
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smp_rmb();
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for (loop--; loop >= 0; loop--) {
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struct key *key = rcu_dereference(klist->keys[loop]);
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if (key_is_dead(key, limit))
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goto do_gc;
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}
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unlock_dont_gc:
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rcu_read_unlock();
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dont_gc:
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kleave(" [no gc]");
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return;
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do_gc:
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rcu_read_unlock();
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keyring_gc(keyring, limit);
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kleave(" [gc]");
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}
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/*
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* Garbage collect a list of unreferenced, detached keys
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*/
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static noinline void key_gc_unused_keys(struct list_head *keys)
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{
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while (!list_empty(keys)) {
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struct key *key =
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list_entry(keys->next, struct key, graveyard_link);
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list_del(&key->graveyard_link);
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kdebug("- %u", key->serial);
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key_check(key);
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security_key_free(key);
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/* deal with the user's key tracking and quota */
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if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
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spin_lock(&key->user->lock);
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key->user->qnkeys--;
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key->user->qnbytes -= key->quotalen;
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spin_unlock(&key->user->lock);
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}
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atomic_dec(&key->user->nkeys);
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if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
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atomic_dec(&key->user->nikeys);
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key_user_put(key->user);
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/* now throw away the key memory */
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if (key->type->destroy)
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key->type->destroy(key);
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kfree(key->description);
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#ifdef KEY_DEBUGGING
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key->magic = KEY_DEBUG_MAGIC_X;
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#endif
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kmem_cache_free(key_jar, key);
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}
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}
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/*
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* Garbage collector for unused keys.
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*
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* This is done in process context so that we don't have to disable interrupts
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* all over the place. key_put() schedules this rather than trying to do the
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* cleanup itself, which means key_put() doesn't have to sleep.
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*/
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static void key_garbage_collector(struct work_struct *work)
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{
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static LIST_HEAD(graveyard);
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static u8 gc_state; /* Internal persistent state */
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#define KEY_GC_REAP_AGAIN 0x01 /* - Need another cycle */
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#define KEY_GC_REAPING_LINKS 0x02 /* - We need to reap links */
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#define KEY_GC_SET_TIMER 0x04 /* - We need to restart the timer */
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#define KEY_GC_REAPING_DEAD_1 0x10 /* - We need to mark dead keys */
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#define KEY_GC_REAPING_DEAD_2 0x20 /* - We need to reap dead key links */
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#define KEY_GC_REAPING_DEAD_3 0x40 /* - We need to reap dead keys */
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#define KEY_GC_FOUND_DEAD_KEY 0x80 /* - We found at least one dead key */
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struct rb_node *cursor;
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struct key *key;
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time_t new_timer, limit;
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kenter("[%lx,%x]", key_gc_flags, gc_state);
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limit = current_kernel_time().tv_sec;
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if (limit > key_gc_delay)
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limit -= key_gc_delay;
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else
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limit = key_gc_delay;
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/* Work out what we're going to be doing in this pass */
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gc_state &= KEY_GC_REAPING_DEAD_1 | KEY_GC_REAPING_DEAD_2;
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gc_state <<= 1;
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if (test_and_clear_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags))
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gc_state |= KEY_GC_REAPING_LINKS | KEY_GC_SET_TIMER;
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if (test_and_clear_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags))
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gc_state |= KEY_GC_REAPING_DEAD_1;
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kdebug("new pass %x", gc_state);
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new_timer = LONG_MAX;
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/* As only this function is permitted to remove things from the key
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* serial tree, if cursor is non-NULL then it will always point to a
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* valid node in the tree - even if lock got dropped.
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*/
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spin_lock(&key_serial_lock);
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cursor = rb_first(&key_serial_tree);
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continue_scanning:
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while (cursor) {
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key = rb_entry(cursor, struct key, serial_node);
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cursor = rb_next(cursor);
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if (atomic_read(&key->usage) == 0)
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goto found_unreferenced_key;
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if (unlikely(gc_state & KEY_GC_REAPING_DEAD_1)) {
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if (key->type == key_gc_dead_keytype) {
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gc_state |= KEY_GC_FOUND_DEAD_KEY;
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set_bit(KEY_FLAG_DEAD, &key->flags);
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key->perm = 0;
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goto skip_dead_key;
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}
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}
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if (gc_state & KEY_GC_SET_TIMER) {
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if (key->expiry > limit && key->expiry < new_timer) {
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kdebug("will expire %x in %ld",
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key_serial(key), key->expiry - limit);
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new_timer = key->expiry;
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}
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}
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if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2))
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if (key->type == key_gc_dead_keytype)
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gc_state |= KEY_GC_FOUND_DEAD_KEY;
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if ((gc_state & KEY_GC_REAPING_LINKS) ||
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unlikely(gc_state & KEY_GC_REAPING_DEAD_2)) {
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if (key->type == &key_type_keyring)
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goto found_keyring;
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}
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if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3))
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if (key->type == key_gc_dead_keytype)
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goto destroy_dead_key;
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skip_dead_key:
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if (spin_is_contended(&key_serial_lock) || need_resched())
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goto contended;
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}
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contended:
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spin_unlock(&key_serial_lock);
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maybe_resched:
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if (cursor) {
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cond_resched();
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spin_lock(&key_serial_lock);
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goto continue_scanning;
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}
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/* We've completed the pass. Set the timer if we need to and queue a
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* new cycle if necessary. We keep executing cycles until we find one
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* where we didn't reap any keys.
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*/
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kdebug("pass complete");
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if (gc_state & KEY_GC_SET_TIMER && new_timer != (time_t)LONG_MAX) {
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new_timer += key_gc_delay;
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key_schedule_gc(new_timer);
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}
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if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2) ||
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!list_empty(&graveyard)) {
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/* Make sure that all pending keyring payload destructions are
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* fulfilled and that people aren't now looking at dead or
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* dying keys that they don't have a reference upon or a link
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* to.
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*/
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kdebug("gc sync");
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synchronize_rcu();
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}
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if (!list_empty(&graveyard)) {
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kdebug("gc keys");
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key_gc_unused_keys(&graveyard);
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}
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if (unlikely(gc_state & (KEY_GC_REAPING_DEAD_1 |
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KEY_GC_REAPING_DEAD_2))) {
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if (!(gc_state & KEY_GC_FOUND_DEAD_KEY)) {
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/* No remaining dead keys: short circuit the remaining
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* keytype reap cycles.
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*/
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kdebug("dead short");
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gc_state &= ~(KEY_GC_REAPING_DEAD_1 | KEY_GC_REAPING_DEAD_2);
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gc_state |= KEY_GC_REAPING_DEAD_3;
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} else {
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gc_state |= KEY_GC_REAP_AGAIN;
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}
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}
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if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) {
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kdebug("dead wake");
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smp_mb();
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clear_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags);
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wake_up_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE);
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}
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if (gc_state & KEY_GC_REAP_AGAIN)
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schedule_work(&key_gc_work);
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kleave(" [end %x]", gc_state);
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return;
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/* We found an unreferenced key - once we've removed it from the tree,
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* we can safely drop the lock.
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*/
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found_unreferenced_key:
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kdebug("unrefd key %d", key->serial);
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rb_erase(&key->serial_node, &key_serial_tree);
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spin_unlock(&key_serial_lock);
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list_add_tail(&key->graveyard_link, &graveyard);
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gc_state |= KEY_GC_REAP_AGAIN;
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goto maybe_resched;
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/* We found a keyring and we need to check the payload for links to
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* dead or expired keys. We don't flag another reap immediately as we
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* have to wait for the old payload to be destroyed by RCU before we
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* can reap the keys to which it refers.
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*/
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found_keyring:
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spin_unlock(&key_serial_lock);
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kdebug("scan keyring %d", key->serial);
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key_gc_keyring(key, limit);
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goto maybe_resched;
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/* We found a dead key that is still referenced. Reset its type and
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* destroy its payload with its semaphore held.
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*/
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destroy_dead_key:
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spin_unlock(&key_serial_lock);
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kdebug("destroy key %d", key->serial);
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down_write(&key->sem);
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key->type = &key_type_dead;
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if (key_gc_dead_keytype->destroy)
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key_gc_dead_keytype->destroy(key);
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memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
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up_write(&key->sem);
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goto maybe_resched;
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}
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