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/* 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;
}
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