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5d135440 DH |
1 | /* Key garbage collector |
2 | * | |
3 | * Copyright (C) 2009 Red Hat, Inc. All Rights Reserved. | |
4 | * Written by David Howells (dhowells@redhat.com) | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU General Public Licence | |
8 | * as published by the Free Software Foundation; either version | |
9 | * 2 of the Licence, or (at your option) any later version. | |
10 | */ | |
11 | ||
12 | #include <linux/module.h> | |
13 | #include <keys/keyring-type.h> | |
14 | #include "internal.h" | |
15 | ||
16 | /* | |
17 | * Delay between key revocation/expiry in seconds | |
18 | */ | |
19 | unsigned key_gc_delay = 5 * 60; | |
20 | ||
21 | /* | |
22 | * Reaper | |
23 | */ | |
24 | static void key_gc_timer_func(unsigned long); | |
25 | static void key_garbage_collector(struct work_struct *); | |
26 | static DEFINE_TIMER(key_gc_timer, key_gc_timer_func, 0, 0); | |
27 | static DECLARE_WORK(key_gc_work, key_garbage_collector); | |
28 | static key_serial_t key_gc_cursor; /* the last key the gc considered */ | |
29 | static unsigned long key_gc_executing; | |
30 | static time_t key_gc_next_run = LONG_MAX; | |
31 | ||
32 | /* | |
33 | * Schedule a garbage collection run | |
34 | * - precision isn't particularly important | |
35 | */ | |
36 | void key_schedule_gc(time_t gc_at) | |
37 | { | |
38 | unsigned long expires; | |
39 | time_t now = current_kernel_time().tv_sec; | |
40 | ||
41 | kenter("%ld", gc_at - now); | |
42 | ||
43 | gc_at += key_gc_delay; | |
44 | ||
45 | if (now >= gc_at) { | |
46 | schedule_work(&key_gc_work); | |
47 | } else if (gc_at < key_gc_next_run) { | |
48 | expires = jiffies + (gc_at - now) * HZ; | |
49 | mod_timer(&key_gc_timer, expires); | |
50 | } | |
51 | } | |
52 | ||
53 | /* | |
54 | * The garbage collector timer kicked off | |
55 | */ | |
56 | static void key_gc_timer_func(unsigned long data) | |
57 | { | |
58 | kenter(""); | |
59 | key_gc_next_run = LONG_MAX; | |
60 | schedule_work(&key_gc_work); | |
61 | } | |
62 | ||
63 | /* | |
64 | * Garbage collect pointers from a keyring | |
65 | * - return true if we altered the keyring | |
66 | */ | |
67 | static bool key_gc_keyring(struct key *keyring, time_t limit) | |
ee18d64c | 68 | __releases(key_serial_lock) |
5d135440 DH |
69 | { |
70 | struct keyring_list *klist; | |
71 | struct key *key; | |
72 | int loop; | |
73 | ||
74 | kenter("%x", key_serial(keyring)); | |
75 | ||
76 | if (test_bit(KEY_FLAG_REVOKED, &keyring->flags)) | |
77 | goto dont_gc; | |
78 | ||
79 | /* scan the keyring looking for dead keys */ | |
80 | klist = rcu_dereference(keyring->payload.subscriptions); | |
81 | if (!klist) | |
82 | goto dont_gc; | |
83 | ||
84 | for (loop = klist->nkeys - 1; loop >= 0; loop--) { | |
85 | key = klist->keys[loop]; | |
86 | if (test_bit(KEY_FLAG_DEAD, &key->flags) || | |
87 | (key->expiry > 0 && key->expiry <= limit)) | |
88 | goto do_gc; | |
89 | } | |
90 | ||
91 | dont_gc: | |
92 | kleave(" = false"); | |
93 | return false; | |
94 | ||
95 | do_gc: | |
96 | key_gc_cursor = keyring->serial; | |
97 | key_get(keyring); | |
98 | spin_unlock(&key_serial_lock); | |
99 | keyring_gc(keyring, limit); | |
100 | key_put(keyring); | |
101 | kleave(" = true"); | |
102 | return true; | |
103 | } | |
104 | ||
105 | /* | |
106 | * Garbage collector for keys | |
107 | * - this involves scanning the keyrings for dead, expired and revoked keys | |
108 | * that have overstayed their welcome | |
109 | */ | |
110 | static void key_garbage_collector(struct work_struct *work) | |
111 | { | |
112 | struct rb_node *rb; | |
113 | key_serial_t cursor; | |
114 | struct key *key, *xkey; | |
115 | time_t new_timer = LONG_MAX, limit; | |
116 | ||
117 | kenter(""); | |
118 | ||
119 | if (test_and_set_bit(0, &key_gc_executing)) { | |
120 | key_schedule_gc(current_kernel_time().tv_sec); | |
121 | return; | |
122 | } | |
123 | ||
124 | limit = current_kernel_time().tv_sec; | |
125 | if (limit > key_gc_delay) | |
126 | limit -= key_gc_delay; | |
127 | else | |
128 | limit = key_gc_delay; | |
129 | ||
130 | spin_lock(&key_serial_lock); | |
131 | ||
132 | if (RB_EMPTY_ROOT(&key_serial_tree)) | |
133 | goto reached_the_end; | |
134 | ||
135 | cursor = key_gc_cursor; | |
136 | if (cursor < 0) | |
137 | cursor = 0; | |
138 | ||
139 | /* find the first key above the cursor */ | |
140 | key = NULL; | |
141 | rb = key_serial_tree.rb_node; | |
142 | while (rb) { | |
143 | xkey = rb_entry(rb, struct key, serial_node); | |
144 | if (cursor < xkey->serial) { | |
145 | key = xkey; | |
146 | rb = rb->rb_left; | |
147 | } else if (cursor > xkey->serial) { | |
148 | rb = rb->rb_right; | |
149 | } else { | |
150 | rb = rb_next(rb); | |
151 | if (!rb) | |
152 | goto reached_the_end; | |
153 | key = rb_entry(rb, struct key, serial_node); | |
154 | break; | |
155 | } | |
156 | } | |
157 | ||
158 | if (!key) | |
159 | goto reached_the_end; | |
160 | ||
161 | /* trawl through the keys looking for keyrings */ | |
162 | for (;;) { | |
163 | if (key->expiry > 0 && key->expiry < new_timer) | |
164 | new_timer = key->expiry; | |
165 | ||
166 | if (key->type == &key_type_keyring && | |
167 | key_gc_keyring(key, limit)) { | |
168 | /* the gc ate our lock */ | |
169 | schedule_work(&key_gc_work); | |
170 | goto no_unlock; | |
171 | } | |
172 | ||
173 | rb = rb_next(&key->serial_node); | |
174 | if (!rb) { | |
175 | key_gc_cursor = 0; | |
176 | break; | |
177 | } | |
178 | key = rb_entry(rb, struct key, serial_node); | |
179 | } | |
180 | ||
181 | out: | |
182 | spin_unlock(&key_serial_lock); | |
183 | no_unlock: | |
184 | clear_bit(0, &key_gc_executing); | |
185 | if (new_timer < LONG_MAX) | |
186 | key_schedule_gc(new_timer); | |
187 | ||
188 | kleave(""); | |
189 | return; | |
190 | ||
191 | reached_the_end: | |
192 | key_gc_cursor = 0; | |
193 | goto out; | |
194 | } |