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55834c59 AP |
1 | /* |
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 | */ | |
40 | struct 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 | ||
48 | static bool qlist_empty(struct qlist_head *q) | |
49 | { | |
50 | return !q->head; | |
51 | } | |
52 | ||
53 | static void qlist_init(struct qlist_head *q) | |
54 | { | |
55 | q->head = q->tail = NULL; | |
56 | q->bytes = 0; | |
57 | } | |
58 | ||
59 | static 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 | ||
71 | static 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 | ||
64abdcb2 DV |
89 | #define QUARANTINE_PERCPU_SIZE (1 << 20) |
90 | #define QUARANTINE_BATCHES \ | |
91 | (1024 > 4 * CONFIG_NR_CPUS ? 1024 : 4 * CONFIG_NR_CPUS) | |
55834c59 AP |
92 | |
93 | /* | |
94 | * The object quarantine consists of per-cpu queues and a global queue, | |
95 | * guarded by quarantine_lock. | |
96 | */ | |
97 | static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine); | |
98 | ||
64abdcb2 DV |
99 | /* Round-robin FIFO array of batches. */ |
100 | static struct qlist_head global_quarantine[QUARANTINE_BATCHES]; | |
101 | static int quarantine_head; | |
102 | static int quarantine_tail; | |
103 | /* Total size of all objects in global_quarantine across all batches. */ | |
104 | static unsigned long quarantine_size; | |
55834c59 AP |
105 | static DEFINE_SPINLOCK(quarantine_lock); |
106 | ||
107 | /* Maximum size of the global queue. */ | |
64abdcb2 DV |
108 | static unsigned long quarantine_max_size; |
109 | ||
110 | /* | |
111 | * Target size of a batch in global_quarantine. | |
112 | * Usually equal to QUARANTINE_PERCPU_SIZE unless we have too much RAM. | |
113 | */ | |
114 | static unsigned long quarantine_batch_size; | |
55834c59 AP |
115 | |
116 | /* | |
117 | * The fraction of physical memory the quarantine is allowed to occupy. | |
118 | * Quarantine doesn't support memory shrinker with SLAB allocator, so we keep | |
119 | * the ratio low to avoid OOM. | |
120 | */ | |
121 | #define QUARANTINE_FRACTION 32 | |
122 | ||
55834c59 AP |
123 | static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink) |
124 | { | |
125 | return virt_to_head_page(qlink)->slab_cache; | |
126 | } | |
127 | ||
128 | static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache) | |
129 | { | |
130 | struct kasan_free_meta *free_info = | |
131 | container_of(qlink, struct kasan_free_meta, | |
132 | quarantine_link); | |
133 | ||
134 | return ((void *)free_info) - cache->kasan_info.free_meta_offset; | |
135 | } | |
136 | ||
137 | static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache) | |
138 | { | |
139 | void *object = qlink_to_object(qlink, cache); | |
55834c59 AP |
140 | unsigned long flags; |
141 | ||
f7376aed AR |
142 | if (IS_ENABLED(CONFIG_SLAB)) |
143 | local_irq_save(flags); | |
144 | ||
55834c59 | 145 | ___cache_free(cache, object, _THIS_IP_); |
f7376aed AR |
146 | |
147 | if (IS_ENABLED(CONFIG_SLAB)) | |
148 | local_irq_restore(flags); | |
55834c59 AP |
149 | } |
150 | ||
151 | static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache) | |
152 | { | |
153 | struct qlist_node *qlink; | |
154 | ||
155 | if (unlikely(qlist_empty(q))) | |
156 | return; | |
157 | ||
158 | qlink = q->head; | |
159 | while (qlink) { | |
160 | struct kmem_cache *obj_cache = | |
161 | cache ? cache : qlink_to_cache(qlink); | |
162 | struct qlist_node *next = qlink->next; | |
163 | ||
164 | qlink_free(qlink, obj_cache); | |
165 | qlink = next; | |
166 | } | |
167 | qlist_init(q); | |
168 | } | |
169 | ||
170 | void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache) | |
171 | { | |
172 | unsigned long flags; | |
173 | struct qlist_head *q; | |
174 | struct qlist_head temp = QLIST_INIT; | |
175 | ||
176 | local_irq_save(flags); | |
177 | ||
178 | q = this_cpu_ptr(&cpu_quarantine); | |
179 | qlist_put(q, &info->quarantine_link, cache->size); | |
180 | if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) | |
181 | qlist_move_all(q, &temp); | |
182 | ||
183 | local_irq_restore(flags); | |
184 | ||
185 | if (unlikely(!qlist_empty(&temp))) { | |
186 | spin_lock_irqsave(&quarantine_lock, flags); | |
64abdcb2 DV |
187 | WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes); |
188 | qlist_move_all(&temp, &global_quarantine[quarantine_tail]); | |
189 | if (global_quarantine[quarantine_tail].bytes >= | |
190 | READ_ONCE(quarantine_batch_size)) { | |
191 | int new_tail; | |
192 | ||
193 | new_tail = quarantine_tail + 1; | |
194 | if (new_tail == QUARANTINE_BATCHES) | |
195 | new_tail = 0; | |
196 | if (new_tail != quarantine_head) | |
197 | quarantine_tail = new_tail; | |
198 | } | |
55834c59 AP |
199 | spin_unlock_irqrestore(&quarantine_lock, flags); |
200 | } | |
201 | } | |
202 | ||
203 | void quarantine_reduce(void) | |
204 | { | |
64abdcb2 | 205 | size_t total_size, new_quarantine_size, percpu_quarantines; |
55834c59 AP |
206 | unsigned long flags; |
207 | struct qlist_head to_free = QLIST_INIT; | |
55834c59 | 208 | |
64abdcb2 DV |
209 | if (likely(READ_ONCE(quarantine_size) <= |
210 | READ_ONCE(quarantine_max_size))) | |
55834c59 AP |
211 | return; |
212 | ||
213 | spin_lock_irqsave(&quarantine_lock, flags); | |
214 | ||
215 | /* | |
216 | * Update quarantine size in case of hotplug. Allocate a fraction of | |
217 | * the installed memory to quarantine minus per-cpu queue limits. | |
218 | */ | |
64abdcb2 | 219 | total_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) / |
55834c59 | 220 | QUARANTINE_FRACTION; |
c3cee372 | 221 | percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus(); |
64abdcb2 DV |
222 | new_quarantine_size = (total_size < percpu_quarantines) ? |
223 | 0 : total_size - percpu_quarantines; | |
224 | WRITE_ONCE(quarantine_max_size, new_quarantine_size); | |
225 | /* Aim at consuming at most 1/2 of slots in quarantine. */ | |
226 | WRITE_ONCE(quarantine_batch_size, max((size_t)QUARANTINE_PERCPU_SIZE, | |
227 | 2 * total_size / QUARANTINE_BATCHES)); | |
228 | ||
229 | if (likely(quarantine_size > quarantine_max_size)) { | |
230 | qlist_move_all(&global_quarantine[quarantine_head], &to_free); | |
231 | WRITE_ONCE(quarantine_size, quarantine_size - to_free.bytes); | |
232 | quarantine_head++; | |
233 | if (quarantine_head == QUARANTINE_BATCHES) | |
234 | quarantine_head = 0; | |
55834c59 | 235 | } |
55834c59 AP |
236 | |
237 | spin_unlock_irqrestore(&quarantine_lock, flags); | |
238 | ||
239 | qlist_free_all(&to_free, NULL); | |
240 | } | |
241 | ||
242 | static void qlist_move_cache(struct qlist_head *from, | |
243 | struct qlist_head *to, | |
244 | struct kmem_cache *cache) | |
245 | { | |
0ab686d8 | 246 | struct qlist_node *curr; |
55834c59 AP |
247 | |
248 | if (unlikely(qlist_empty(from))) | |
249 | return; | |
250 | ||
251 | curr = from->head; | |
0ab686d8 | 252 | qlist_init(from); |
55834c59 | 253 | while (curr) { |
0ab686d8 JK |
254 | struct qlist_node *next = curr->next; |
255 | struct kmem_cache *obj_cache = qlink_to_cache(curr); | |
256 | ||
257 | if (obj_cache == cache) | |
258 | qlist_put(to, curr, obj_cache->size); | |
259 | else | |
260 | qlist_put(from, curr, obj_cache->size); | |
261 | ||
262 | curr = next; | |
55834c59 AP |
263 | } |
264 | } | |
265 | ||
266 | static void per_cpu_remove_cache(void *arg) | |
267 | { | |
268 | struct kmem_cache *cache = arg; | |
269 | struct qlist_head to_free = QLIST_INIT; | |
270 | struct qlist_head *q; | |
271 | ||
272 | q = this_cpu_ptr(&cpu_quarantine); | |
273 | qlist_move_cache(q, &to_free, cache); | |
274 | qlist_free_all(&to_free, cache); | |
275 | } | |
276 | ||
f9fa1d91 | 277 | /* Free all quarantined objects belonging to cache. */ |
55834c59 AP |
278 | void quarantine_remove_cache(struct kmem_cache *cache) |
279 | { | |
64abdcb2 | 280 | unsigned long flags, i; |
55834c59 AP |
281 | struct qlist_head to_free = QLIST_INIT; |
282 | ||
283 | on_each_cpu(per_cpu_remove_cache, cache, 1); | |
284 | ||
285 | spin_lock_irqsave(&quarantine_lock, flags); | |
64abdcb2 DV |
286 | for (i = 0; i < QUARANTINE_BATCHES; i++) |
287 | qlist_move_cache(&global_quarantine[i], &to_free, cache); | |
55834c59 AP |
288 | spin_unlock_irqrestore(&quarantine_lock, flags); |
289 | ||
290 | qlist_free_all(&to_free, cache); | |
291 | } |