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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 | /* 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]");
}
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