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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> | |
ce5bec54 | 28 | #include <linux/srcu.h> |
55834c59 AP |
29 | #include <linux/string.h> |
30 | #include <linux/types.h> | |
31 | ||
32 | #include "../slab.h" | |
33 | #include "kasan.h" | |
34 | ||
35 | /* Data structure and operations for quarantine queues. */ | |
36 | ||
37 | /* | |
38 | * Each queue is a signle-linked list, which also stores the total size of | |
39 | * objects inside of it. | |
40 | */ | |
41 | struct qlist_head { | |
42 | struct qlist_node *head; | |
43 | struct qlist_node *tail; | |
44 | size_t bytes; | |
45 | }; | |
46 | ||
47 | #define QLIST_INIT { NULL, NULL, 0 } | |
48 | ||
49 | static bool qlist_empty(struct qlist_head *q) | |
50 | { | |
51 | return !q->head; | |
52 | } | |
53 | ||
54 | static void qlist_init(struct qlist_head *q) | |
55 | { | |
56 | q->head = q->tail = NULL; | |
57 | q->bytes = 0; | |
58 | } | |
59 | ||
60 | static void qlist_put(struct qlist_head *q, struct qlist_node *qlink, | |
61 | size_t size) | |
62 | { | |
63 | if (unlikely(qlist_empty(q))) | |
64 | q->head = qlink; | |
65 | else | |
66 | q->tail->next = qlink; | |
67 | q->tail = qlink; | |
68 | qlink->next = NULL; | |
69 | q->bytes += size; | |
70 | } | |
71 | ||
72 | static void qlist_move_all(struct qlist_head *from, struct qlist_head *to) | |
73 | { | |
74 | if (unlikely(qlist_empty(from))) | |
75 | return; | |
76 | ||
77 | if (qlist_empty(to)) { | |
78 | *to = *from; | |
79 | qlist_init(from); | |
80 | return; | |
81 | } | |
82 | ||
83 | to->tail->next = from->head; | |
84 | to->tail = from->tail; | |
85 | to->bytes += from->bytes; | |
86 | ||
87 | qlist_init(from); | |
88 | } | |
89 | ||
64abdcb2 DV |
90 | #define QUARANTINE_PERCPU_SIZE (1 << 20) |
91 | #define QUARANTINE_BATCHES \ | |
92 | (1024 > 4 * CONFIG_NR_CPUS ? 1024 : 4 * CONFIG_NR_CPUS) | |
55834c59 AP |
93 | |
94 | /* | |
95 | * The object quarantine consists of per-cpu queues and a global queue, | |
96 | * guarded by quarantine_lock. | |
97 | */ | |
98 | static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine); | |
99 | ||
64abdcb2 DV |
100 | /* Round-robin FIFO array of batches. */ |
101 | static struct qlist_head global_quarantine[QUARANTINE_BATCHES]; | |
102 | static int quarantine_head; | |
103 | static int quarantine_tail; | |
104 | /* Total size of all objects in global_quarantine across all batches. */ | |
105 | static unsigned long quarantine_size; | |
55834c59 | 106 | static DEFINE_SPINLOCK(quarantine_lock); |
ce5bec54 | 107 | DEFINE_STATIC_SRCU(remove_cache_srcu); |
55834c59 AP |
108 | |
109 | /* Maximum size of the global queue. */ | |
64abdcb2 DV |
110 | static unsigned long quarantine_max_size; |
111 | ||
112 | /* | |
113 | * Target size of a batch in global_quarantine. | |
114 | * Usually equal to QUARANTINE_PERCPU_SIZE unless we have too much RAM. | |
115 | */ | |
116 | static unsigned long quarantine_batch_size; | |
55834c59 AP |
117 | |
118 | /* | |
119 | * The fraction of physical memory the quarantine is allowed to occupy. | |
120 | * Quarantine doesn't support memory shrinker with SLAB allocator, so we keep | |
121 | * the ratio low to avoid OOM. | |
122 | */ | |
123 | #define QUARANTINE_FRACTION 32 | |
124 | ||
55834c59 AP |
125 | static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink) |
126 | { | |
127 | return virt_to_head_page(qlink)->slab_cache; | |
128 | } | |
129 | ||
130 | static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache) | |
131 | { | |
132 | struct kasan_free_meta *free_info = | |
133 | container_of(qlink, struct kasan_free_meta, | |
134 | quarantine_link); | |
135 | ||
136 | return ((void *)free_info) - cache->kasan_info.free_meta_offset; | |
137 | } | |
138 | ||
139 | static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache) | |
140 | { | |
141 | void *object = qlink_to_object(qlink, cache); | |
55834c59 AP |
142 | unsigned long flags; |
143 | ||
f7376aed AR |
144 | if (IS_ENABLED(CONFIG_SLAB)) |
145 | local_irq_save(flags); | |
146 | ||
55834c59 | 147 | ___cache_free(cache, object, _THIS_IP_); |
f7376aed AR |
148 | |
149 | if (IS_ENABLED(CONFIG_SLAB)) | |
150 | local_irq_restore(flags); | |
55834c59 AP |
151 | } |
152 | ||
153 | static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache) | |
154 | { | |
155 | struct qlist_node *qlink; | |
156 | ||
157 | if (unlikely(qlist_empty(q))) | |
158 | return; | |
159 | ||
160 | qlink = q->head; | |
161 | while (qlink) { | |
162 | struct kmem_cache *obj_cache = | |
163 | cache ? cache : qlink_to_cache(qlink); | |
164 | struct qlist_node *next = qlink->next; | |
165 | ||
166 | qlink_free(qlink, obj_cache); | |
167 | qlink = next; | |
168 | } | |
169 | qlist_init(q); | |
170 | } | |
171 | ||
172 | void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache) | |
173 | { | |
174 | unsigned long flags; | |
175 | struct qlist_head *q; | |
176 | struct qlist_head temp = QLIST_INIT; | |
177 | ||
ce5bec54 DV |
178 | /* |
179 | * Note: irq must be disabled until after we move the batch to the | |
180 | * global quarantine. Otherwise quarantine_remove_cache() can miss | |
181 | * some objects belonging to the cache if they are in our local temp | |
182 | * list. quarantine_remove_cache() executes on_each_cpu() at the | |
183 | * beginning which ensures that it either sees the objects in per-cpu | |
184 | * lists or in the global quarantine. | |
185 | */ | |
55834c59 AP |
186 | local_irq_save(flags); |
187 | ||
188 | q = this_cpu_ptr(&cpu_quarantine); | |
189 | qlist_put(q, &info->quarantine_link, cache->size); | |
ce5bec54 | 190 | if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) { |
55834c59 AP |
191 | qlist_move_all(q, &temp); |
192 | ||
ce5bec54 | 193 | spin_lock(&quarantine_lock); |
64abdcb2 DV |
194 | WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes); |
195 | qlist_move_all(&temp, &global_quarantine[quarantine_tail]); | |
196 | if (global_quarantine[quarantine_tail].bytes >= | |
197 | READ_ONCE(quarantine_batch_size)) { | |
198 | int new_tail; | |
199 | ||
200 | new_tail = quarantine_tail + 1; | |
201 | if (new_tail == QUARANTINE_BATCHES) | |
202 | new_tail = 0; | |
203 | if (new_tail != quarantine_head) | |
204 | quarantine_tail = new_tail; | |
205 | } | |
ce5bec54 | 206 | spin_unlock(&quarantine_lock); |
55834c59 | 207 | } |
ce5bec54 DV |
208 | |
209 | local_irq_restore(flags); | |
55834c59 AP |
210 | } |
211 | ||
212 | void quarantine_reduce(void) | |
213 | { | |
64abdcb2 | 214 | size_t total_size, new_quarantine_size, percpu_quarantines; |
55834c59 | 215 | unsigned long flags; |
ce5bec54 | 216 | int srcu_idx; |
55834c59 | 217 | struct qlist_head to_free = QLIST_INIT; |
55834c59 | 218 | |
64abdcb2 DV |
219 | if (likely(READ_ONCE(quarantine_size) <= |
220 | READ_ONCE(quarantine_max_size))) | |
55834c59 AP |
221 | return; |
222 | ||
ce5bec54 DV |
223 | /* |
224 | * srcu critical section ensures that quarantine_remove_cache() | |
225 | * will not miss objects belonging to the cache while they are in our | |
226 | * local to_free list. srcu is chosen because (1) it gives us private | |
227 | * grace period domain that does not interfere with anything else, | |
228 | * and (2) it allows synchronize_srcu() to return without waiting | |
229 | * if there are no pending read critical sections (which is the | |
230 | * expected case). | |
231 | */ | |
232 | srcu_idx = srcu_read_lock(&remove_cache_srcu); | |
55834c59 AP |
233 | spin_lock_irqsave(&quarantine_lock, flags); |
234 | ||
235 | /* | |
236 | * Update quarantine size in case of hotplug. Allocate a fraction of | |
237 | * the installed memory to quarantine minus per-cpu queue limits. | |
238 | */ | |
64abdcb2 | 239 | total_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) / |
55834c59 | 240 | QUARANTINE_FRACTION; |
c3cee372 | 241 | percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus(); |
64abdcb2 DV |
242 | new_quarantine_size = (total_size < percpu_quarantines) ? |
243 | 0 : total_size - percpu_quarantines; | |
244 | WRITE_ONCE(quarantine_max_size, new_quarantine_size); | |
245 | /* Aim at consuming at most 1/2 of slots in quarantine. */ | |
246 | WRITE_ONCE(quarantine_batch_size, max((size_t)QUARANTINE_PERCPU_SIZE, | |
247 | 2 * total_size / QUARANTINE_BATCHES)); | |
248 | ||
249 | if (likely(quarantine_size > quarantine_max_size)) { | |
250 | qlist_move_all(&global_quarantine[quarantine_head], &to_free); | |
251 | WRITE_ONCE(quarantine_size, quarantine_size - to_free.bytes); | |
252 | quarantine_head++; | |
253 | if (quarantine_head == QUARANTINE_BATCHES) | |
254 | quarantine_head = 0; | |
55834c59 | 255 | } |
55834c59 AP |
256 | |
257 | spin_unlock_irqrestore(&quarantine_lock, flags); | |
258 | ||
259 | qlist_free_all(&to_free, NULL); | |
ce5bec54 | 260 | srcu_read_unlock(&remove_cache_srcu, srcu_idx); |
55834c59 AP |
261 | } |
262 | ||
263 | static void qlist_move_cache(struct qlist_head *from, | |
264 | struct qlist_head *to, | |
265 | struct kmem_cache *cache) | |
266 | { | |
0ab686d8 | 267 | struct qlist_node *curr; |
55834c59 AP |
268 | |
269 | if (unlikely(qlist_empty(from))) | |
270 | return; | |
271 | ||
272 | curr = from->head; | |
0ab686d8 | 273 | qlist_init(from); |
55834c59 | 274 | while (curr) { |
0ab686d8 JK |
275 | struct qlist_node *next = curr->next; |
276 | struct kmem_cache *obj_cache = qlink_to_cache(curr); | |
277 | ||
278 | if (obj_cache == cache) | |
279 | qlist_put(to, curr, obj_cache->size); | |
280 | else | |
281 | qlist_put(from, curr, obj_cache->size); | |
282 | ||
283 | curr = next; | |
55834c59 AP |
284 | } |
285 | } | |
286 | ||
287 | static void per_cpu_remove_cache(void *arg) | |
288 | { | |
289 | struct kmem_cache *cache = arg; | |
290 | struct qlist_head to_free = QLIST_INIT; | |
291 | struct qlist_head *q; | |
292 | ||
293 | q = this_cpu_ptr(&cpu_quarantine); | |
294 | qlist_move_cache(q, &to_free, cache); | |
295 | qlist_free_all(&to_free, cache); | |
296 | } | |
297 | ||
f9fa1d91 | 298 | /* Free all quarantined objects belonging to cache. */ |
55834c59 AP |
299 | void quarantine_remove_cache(struct kmem_cache *cache) |
300 | { | |
64abdcb2 | 301 | unsigned long flags, i; |
55834c59 AP |
302 | struct qlist_head to_free = QLIST_INIT; |
303 | ||
ce5bec54 DV |
304 | /* |
305 | * Must be careful to not miss any objects that are being moved from | |
306 | * per-cpu list to the global quarantine in quarantine_put(), | |
307 | * nor objects being freed in quarantine_reduce(). on_each_cpu() | |
308 | * achieves the first goal, while synchronize_srcu() achieves the | |
309 | * second. | |
310 | */ | |
55834c59 AP |
311 | on_each_cpu(per_cpu_remove_cache, cache, 1); |
312 | ||
313 | spin_lock_irqsave(&quarantine_lock, flags); | |
68fd814a DV |
314 | for (i = 0; i < QUARANTINE_BATCHES; i++) { |
315 | if (qlist_empty(&global_quarantine[i])) | |
316 | continue; | |
64abdcb2 | 317 | qlist_move_cache(&global_quarantine[i], &to_free, cache); |
68fd814a DV |
318 | /* Scanning whole quarantine can take a while. */ |
319 | spin_unlock_irqrestore(&quarantine_lock, flags); | |
320 | cond_resched(); | |
321 | spin_lock_irqsave(&quarantine_lock, flags); | |
322 | } | |
55834c59 AP |
323 | spin_unlock_irqrestore(&quarantine_lock, flags); |
324 | ||
325 | qlist_free_all(&to_free, cache); | |
ce5bec54 DV |
326 | |
327 | synchronize_srcu(&remove_cache_srcu); | |
55834c59 | 328 | } |