1 files changed, 193 insertions, 0 deletions

diff --git a/security/keys/gc.c b/security/keys/gc.c
new file mode 100644
index 000000000000..44adc325e15c
--- /dev/null
+++ b/security/keys/gc.c
@@ -0,0 +1,193 @@
+/* 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)
+{
+        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;
+}