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-rw-r--r--security/keys/gc.c218
1 files changed, 218 insertions, 0 deletions
diff --git a/security/keys/gc.c b/security/keys/gc.c
new file mode 100644
index 00000000000..485fc6233c3
--- /dev/null
+++ b/security/keys/gc.c
@@ -0,0 +1,218 @@
+/* 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
+ * - 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 */
+ 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, 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 > now && key->expiry < new_timer) {
+ kdebug("will expire %x in %ld",
+ key_serial(key), key->expiry - now);
+ 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]");
+}