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Alexander Potapenko55834c52016-05-20 16:59:11 -07001/*
2 * KASAN quarantine.
3 *
4 * Author: Alexander Potapenko <glider@google.com>
5 * Copyright (C) 2016 Google, Inc.
6 *
7 * Based on code by Dmitry Chernenkov.
8 *
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License
11 * version 2 as published by the Free Software Foundation.
12 *
13 * This program is distributed in the hope that it will be useful, but
14 * WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * General Public License for more details.
17 *
18 */
19
20#include <linux/gfp.h>
21#include <linux/hash.h>
22#include <linux/kernel.h>
23#include <linux/mm.h>
24#include <linux/percpu.h>
25#include <linux/printk.h>
26#include <linux/shrinker.h>
27#include <linux/slab.h>
28#include <linux/string.h>
29#include <linux/types.h>
30
31#include "../slab.h"
32#include "kasan.h"
33
34/* Data structure and operations for quarantine queues. */
35
36/*
37 * Each queue is a signle-linked list, which also stores the total size of
38 * objects inside of it.
39 */
40struct qlist_head {
41 struct qlist_node *head;
42 struct qlist_node *tail;
43 size_t bytes;
44};
45
46#define QLIST_INIT { NULL, NULL, 0 }
47
48static bool qlist_empty(struct qlist_head *q)
49{
50 return !q->head;
51}
52
53static void qlist_init(struct qlist_head *q)
54{
55 q->head = q->tail = NULL;
56 q->bytes = 0;
57}
58
59static void qlist_put(struct qlist_head *q, struct qlist_node *qlink,
60 size_t size)
61{
62 if (unlikely(qlist_empty(q)))
63 q->head = qlink;
64 else
65 q->tail->next = qlink;
66 q->tail = qlink;
67 qlink->next = NULL;
68 q->bytes += size;
69}
70
71static void qlist_move_all(struct qlist_head *from, struct qlist_head *to)
72{
73 if (unlikely(qlist_empty(from)))
74 return;
75
76 if (qlist_empty(to)) {
77 *to = *from;
78 qlist_init(from);
79 return;
80 }
81
82 to->tail->next = from->head;
83 to->tail = from->tail;
84 to->bytes += from->bytes;
85
86 qlist_init(from);
87}
88
89static void qlist_move(struct qlist_head *from, struct qlist_node *last,
90 struct qlist_head *to, size_t size)
91{
92 if (unlikely(last == from->tail)) {
93 qlist_move_all(from, to);
94 return;
95 }
96 if (qlist_empty(to))
97 to->head = from->head;
98 else
99 to->tail->next = from->head;
100 to->tail = last;
101 from->head = last->next;
102 last->next = NULL;
103 from->bytes -= size;
104 to->bytes += size;
105}
106
107
108/*
109 * The object quarantine consists of per-cpu queues and a global queue,
110 * guarded by quarantine_lock.
111 */
112static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine);
113
114static struct qlist_head global_quarantine;
115static DEFINE_SPINLOCK(quarantine_lock);
116
117/* Maximum size of the global queue. */
118static unsigned long quarantine_size;
119
120/*
121 * The fraction of physical memory the quarantine is allowed to occupy.
122 * Quarantine doesn't support memory shrinker with SLAB allocator, so we keep
123 * the ratio low to avoid OOM.
124 */
125#define QUARANTINE_FRACTION 32
126
127#define QUARANTINE_LOW_SIZE (READ_ONCE(quarantine_size) * 3 / 4)
128#define QUARANTINE_PERCPU_SIZE (1 << 20)
129
130static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink)
131{
132 return virt_to_head_page(qlink)->slab_cache;
133}
134
135static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache)
136{
137 struct kasan_free_meta *free_info =
138 container_of(qlink, struct kasan_free_meta,
139 quarantine_link);
140
141 return ((void *)free_info) - cache->kasan_info.free_meta_offset;
142}
143
144static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
145{
146 void *object = qlink_to_object(qlink, cache);
Alexander Potapenko55834c52016-05-20 16:59:11 -0700147 unsigned long flags;
148
Andrey Ryabininf7376ae2016-08-02 14:02:46 -0700149 if (IS_ENABLED(CONFIG_SLAB))
150 local_irq_save(flags);
151
Alexander Potapenko55834c52016-05-20 16:59:11 -0700152 ___cache_free(cache, object, _THIS_IP_);
Andrey Ryabininf7376ae2016-08-02 14:02:46 -0700153
154 if (IS_ENABLED(CONFIG_SLAB))
155 local_irq_restore(flags);
Alexander Potapenko55834c52016-05-20 16:59:11 -0700156}
157
158static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache)
159{
160 struct qlist_node *qlink;
161
162 if (unlikely(qlist_empty(q)))
163 return;
164
165 qlink = q->head;
166 while (qlink) {
167 struct kmem_cache *obj_cache =
168 cache ? cache : qlink_to_cache(qlink);
169 struct qlist_node *next = qlink->next;
170
171 qlink_free(qlink, obj_cache);
172 qlink = next;
173 }
174 qlist_init(q);
175}
176
177void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
178{
179 unsigned long flags;
180 struct qlist_head *q;
181 struct qlist_head temp = QLIST_INIT;
182
183 local_irq_save(flags);
184
185 q = this_cpu_ptr(&cpu_quarantine);
186 qlist_put(q, &info->quarantine_link, cache->size);
187 if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE))
188 qlist_move_all(q, &temp);
189
190 local_irq_restore(flags);
191
192 if (unlikely(!qlist_empty(&temp))) {
193 spin_lock_irqsave(&quarantine_lock, flags);
194 qlist_move_all(&temp, &global_quarantine);
195 spin_unlock_irqrestore(&quarantine_lock, flags);
196 }
197}
198
199void quarantine_reduce(void)
200{
Alexander Potapenkoc3cee372016-08-02 14:02:58 -0700201 size_t new_quarantine_size, percpu_quarantines;
Alexander Potapenko55834c52016-05-20 16:59:11 -0700202 unsigned long flags;
203 struct qlist_head to_free = QLIST_INIT;
204 size_t size_to_free = 0;
205 struct qlist_node *last;
206
207 if (likely(READ_ONCE(global_quarantine.bytes) <=
208 READ_ONCE(quarantine_size)))
209 return;
210
211 spin_lock_irqsave(&quarantine_lock, flags);
212
213 /*
214 * Update quarantine size in case of hotplug. Allocate a fraction of
215 * the installed memory to quarantine minus per-cpu queue limits.
216 */
217 new_quarantine_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) /
218 QUARANTINE_FRACTION;
Alexander Potapenkoc3cee372016-08-02 14:02:58 -0700219 percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus();
Alexander Potapenkobcbf0d52016-08-11 15:33:06 -0700220 new_quarantine_size = (new_quarantine_size < percpu_quarantines) ?
221 0 : new_quarantine_size - percpu_quarantines;
Alexander Potapenko55834c52016-05-20 16:59:11 -0700222 WRITE_ONCE(quarantine_size, new_quarantine_size);
223
224 last = global_quarantine.head;
225 while (last) {
226 struct kmem_cache *cache = qlink_to_cache(last);
227
228 size_to_free += cache->size;
229 if (!last->next || size_to_free >
230 global_quarantine.bytes - QUARANTINE_LOW_SIZE)
231 break;
232 last = last->next;
233 }
234 qlist_move(&global_quarantine, last, &to_free, size_to_free);
235
236 spin_unlock_irqrestore(&quarantine_lock, flags);
237
238 qlist_free_all(&to_free, NULL);
239}
240
241static void qlist_move_cache(struct qlist_head *from,
242 struct qlist_head *to,
243 struct kmem_cache *cache)
244{
Joonsoo Kim0ab686d2016-07-14 12:07:17 -0700245 struct qlist_node *curr;
Alexander Potapenko55834c52016-05-20 16:59:11 -0700246
247 if (unlikely(qlist_empty(from)))
248 return;
249
250 curr = from->head;
Joonsoo Kim0ab686d2016-07-14 12:07:17 -0700251 qlist_init(from);
Alexander Potapenko55834c52016-05-20 16:59:11 -0700252 while (curr) {
Joonsoo Kim0ab686d2016-07-14 12:07:17 -0700253 struct qlist_node *next = curr->next;
254 struct kmem_cache *obj_cache = qlink_to_cache(curr);
Alexander Potapenko55834c52016-05-20 16:59:11 -0700255
Joonsoo Kim0ab686d2016-07-14 12:07:17 -0700256 if (obj_cache == cache)
257 qlist_put(to, curr, obj_cache->size);
258 else
259 qlist_put(from, curr, obj_cache->size);
260
261 curr = next;
Alexander Potapenko55834c52016-05-20 16:59:11 -0700262 }
263}
264
265static void per_cpu_remove_cache(void *arg)
266{
267 struct kmem_cache *cache = arg;
268 struct qlist_head to_free = QLIST_INIT;
269 struct qlist_head *q;
270
271 q = this_cpu_ptr(&cpu_quarantine);
272 qlist_move_cache(q, &to_free, cache);
273 qlist_free_all(&to_free, cache);
274}
275
276void quarantine_remove_cache(struct kmem_cache *cache)
277{
278 unsigned long flags;
279 struct qlist_head to_free = QLIST_INIT;
280
281 on_each_cpu(per_cpu_remove_cache, cache, 1);
282
283 spin_lock_irqsave(&quarantine_lock, flags);
284 qlist_move_cache(&global_quarantine, &to_free, cache);
285 spin_unlock_irqrestore(&quarantine_lock, flags);
286
287 qlist_free_all(&to_free, cache);
288}