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e886bf9d | 1 | // SPDX-License-Identifier: GPL-2.0 |
55834c59 AP |
2 | /* |
3 | * KASAN quarantine. | |
4 | * | |
5 | * Author: Alexander Potapenko <glider@google.com> | |
6 | * Copyright (C) 2016 Google, Inc. | |
7 | * | |
8 | * Based on code by Dmitry Chernenkov. | |
55834c59 AP |
9 | */ |
10 | ||
11 | #include <linux/gfp.h> | |
12 | #include <linux/hash.h> | |
13 | #include <linux/kernel.h> | |
14 | #include <linux/mm.h> | |
15 | #include <linux/percpu.h> | |
16 | #include <linux/printk.h> | |
17 | #include <linux/shrinker.h> | |
18 | #include <linux/slab.h> | |
ce5bec54 | 19 | #include <linux/srcu.h> |
55834c59 AP |
20 | #include <linux/string.h> |
21 | #include <linux/types.h> | |
6c82d45c | 22 | #include <linux/cpuhotplug.h> |
55834c59 AP |
23 | |
24 | #include "../slab.h" | |
25 | #include "kasan.h" | |
26 | ||
27 | /* Data structure and operations for quarantine queues. */ | |
28 | ||
29 | /* | |
30 | * Each queue is a signle-linked list, which also stores the total size of | |
31 | * objects inside of it. | |
32 | */ | |
33 | struct qlist_head { | |
34 | struct qlist_node *head; | |
35 | struct qlist_node *tail; | |
36 | size_t bytes; | |
6c82d45c | 37 | bool offline; |
55834c59 AP |
38 | }; |
39 | ||
40 | #define QLIST_INIT { NULL, NULL, 0 } | |
41 | ||
42 | static bool qlist_empty(struct qlist_head *q) | |
43 | { | |
44 | return !q->head; | |
45 | } | |
46 | ||
47 | static void qlist_init(struct qlist_head *q) | |
48 | { | |
49 | q->head = q->tail = NULL; | |
50 | q->bytes = 0; | |
51 | } | |
52 | ||
53 | static void qlist_put(struct qlist_head *q, struct qlist_node *qlink, | |
54 | size_t size) | |
55 | { | |
56 | if (unlikely(qlist_empty(q))) | |
57 | q->head = qlink; | |
58 | else | |
59 | q->tail->next = qlink; | |
60 | q->tail = qlink; | |
61 | qlink->next = NULL; | |
62 | q->bytes += size; | |
63 | } | |
64 | ||
65 | static void qlist_move_all(struct qlist_head *from, struct qlist_head *to) | |
66 | { | |
67 | if (unlikely(qlist_empty(from))) | |
68 | return; | |
69 | ||
70 | if (qlist_empty(to)) { | |
71 | *to = *from; | |
72 | qlist_init(from); | |
73 | return; | |
74 | } | |
75 | ||
76 | to->tail->next = from->head; | |
77 | to->tail = from->tail; | |
78 | to->bytes += from->bytes; | |
79 | ||
80 | qlist_init(from); | |
81 | } | |
82 | ||
64abdcb2 DV |
83 | #define QUARANTINE_PERCPU_SIZE (1 << 20) |
84 | #define QUARANTINE_BATCHES \ | |
85 | (1024 > 4 * CONFIG_NR_CPUS ? 1024 : 4 * CONFIG_NR_CPUS) | |
55834c59 AP |
86 | |
87 | /* | |
88 | * The object quarantine consists of per-cpu queues and a global queue, | |
89 | * guarded by quarantine_lock. | |
90 | */ | |
91 | static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine); | |
92 | ||
64abdcb2 DV |
93 | /* Round-robin FIFO array of batches. */ |
94 | static struct qlist_head global_quarantine[QUARANTINE_BATCHES]; | |
95 | static int quarantine_head; | |
96 | static int quarantine_tail; | |
97 | /* Total size of all objects in global_quarantine across all batches. */ | |
98 | static unsigned long quarantine_size; | |
026d1eaf | 99 | static DEFINE_RAW_SPINLOCK(quarantine_lock); |
ce5bec54 | 100 | DEFINE_STATIC_SRCU(remove_cache_srcu); |
55834c59 AP |
101 | |
102 | /* Maximum size of the global queue. */ | |
64abdcb2 DV |
103 | static unsigned long quarantine_max_size; |
104 | ||
105 | /* | |
106 | * Target size of a batch in global_quarantine. | |
107 | * Usually equal to QUARANTINE_PERCPU_SIZE unless we have too much RAM. | |
108 | */ | |
109 | static unsigned long quarantine_batch_size; | |
55834c59 AP |
110 | |
111 | /* | |
112 | * The fraction of physical memory the quarantine is allowed to occupy. | |
113 | * Quarantine doesn't support memory shrinker with SLAB allocator, so we keep | |
114 | * the ratio low to avoid OOM. | |
115 | */ | |
116 | #define QUARANTINE_FRACTION 32 | |
117 | ||
55834c59 AP |
118 | static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink) |
119 | { | |
120 | return virt_to_head_page(qlink)->slab_cache; | |
121 | } | |
122 | ||
123 | static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache) | |
124 | { | |
125 | struct kasan_free_meta *free_info = | |
126 | container_of(qlink, struct kasan_free_meta, | |
127 | quarantine_link); | |
128 | ||
129 | return ((void *)free_info) - cache->kasan_info.free_meta_offset; | |
130 | } | |
131 | ||
132 | static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache) | |
133 | { | |
134 | void *object = qlink_to_object(qlink, cache); | |
55834c59 AP |
135 | unsigned long flags; |
136 | ||
f7376aed AR |
137 | if (IS_ENABLED(CONFIG_SLAB)) |
138 | local_irq_save(flags); | |
139 | ||
97593cad AK |
140 | /* |
141 | * As the object now gets freed from the quaratine, assume that its | |
142 | * free track is no longer valid. | |
143 | */ | |
e4b7818b | 144 | *(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREE; |
97593cad | 145 | |
55834c59 | 146 | ___cache_free(cache, object, _THIS_IP_); |
f7376aed AR |
147 | |
148 | if (IS_ENABLED(CONFIG_SLAB)) | |
149 | local_irq_restore(flags); | |
55834c59 AP |
150 | } |
151 | ||
152 | static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache) | |
153 | { | |
154 | struct qlist_node *qlink; | |
155 | ||
156 | if (unlikely(qlist_empty(q))) | |
157 | return; | |
158 | ||
159 | qlink = q->head; | |
160 | while (qlink) { | |
161 | struct kmem_cache *obj_cache = | |
162 | cache ? cache : qlink_to_cache(qlink); | |
163 | struct qlist_node *next = qlink->next; | |
164 | ||
165 | qlink_free(qlink, obj_cache); | |
166 | qlink = next; | |
167 | } | |
168 | qlist_init(q); | |
169 | } | |
170 | ||
97593cad | 171 | bool quarantine_put(struct kmem_cache *cache, void *object) |
55834c59 AP |
172 | { |
173 | unsigned long flags; | |
174 | struct qlist_head *q; | |
175 | struct qlist_head temp = QLIST_INIT; | |
6476792f | 176 | struct kasan_free_meta *meta = kasan_get_free_meta(cache, object); |
55834c59 | 177 | |
97593cad AK |
178 | /* |
179 | * If there's no metadata for this object, don't put it into | |
180 | * quarantine. | |
181 | */ | |
182 | if (!meta) | |
183 | return false; | |
184 | ||
ce5bec54 DV |
185 | /* |
186 | * Note: irq must be disabled until after we move the batch to the | |
187 | * global quarantine. Otherwise quarantine_remove_cache() can miss | |
188 | * some objects belonging to the cache if they are in our local temp | |
189 | * list. quarantine_remove_cache() executes on_each_cpu() at the | |
190 | * beginning which ensures that it either sees the objects in per-cpu | |
191 | * lists or in the global quarantine. | |
192 | */ | |
55834c59 AP |
193 | local_irq_save(flags); |
194 | ||
195 | q = this_cpu_ptr(&cpu_quarantine); | |
6c82d45c KYL |
196 | if (q->offline) { |
197 | local_irq_restore(flags); | |
97593cad | 198 | return false; |
6c82d45c | 199 | } |
6476792f | 200 | qlist_put(q, &meta->quarantine_link, cache->size); |
ce5bec54 | 201 | if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) { |
55834c59 AP |
202 | qlist_move_all(q, &temp); |
203 | ||
026d1eaf | 204 | raw_spin_lock(&quarantine_lock); |
64abdcb2 DV |
205 | WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes); |
206 | qlist_move_all(&temp, &global_quarantine[quarantine_tail]); | |
207 | if (global_quarantine[quarantine_tail].bytes >= | |
208 | READ_ONCE(quarantine_batch_size)) { | |
209 | int new_tail; | |
210 | ||
211 | new_tail = quarantine_tail + 1; | |
212 | if (new_tail == QUARANTINE_BATCHES) | |
213 | new_tail = 0; | |
214 | if (new_tail != quarantine_head) | |
215 | quarantine_tail = new_tail; | |
216 | } | |
026d1eaf | 217 | raw_spin_unlock(&quarantine_lock); |
55834c59 | 218 | } |
ce5bec54 DV |
219 | |
220 | local_irq_restore(flags); | |
97593cad AK |
221 | |
222 | return true; | |
55834c59 AP |
223 | } |
224 | ||
225 | void quarantine_reduce(void) | |
226 | { | |
64abdcb2 | 227 | size_t total_size, new_quarantine_size, percpu_quarantines; |
55834c59 | 228 | unsigned long flags; |
ce5bec54 | 229 | int srcu_idx; |
55834c59 | 230 | struct qlist_head to_free = QLIST_INIT; |
55834c59 | 231 | |
64abdcb2 DV |
232 | if (likely(READ_ONCE(quarantine_size) <= |
233 | READ_ONCE(quarantine_max_size))) | |
55834c59 AP |
234 | return; |
235 | ||
ce5bec54 DV |
236 | /* |
237 | * srcu critical section ensures that quarantine_remove_cache() | |
238 | * will not miss objects belonging to the cache while they are in our | |
239 | * local to_free list. srcu is chosen because (1) it gives us private | |
240 | * grace period domain that does not interfere with anything else, | |
241 | * and (2) it allows synchronize_srcu() to return without waiting | |
242 | * if there are no pending read critical sections (which is the | |
243 | * expected case). | |
244 | */ | |
245 | srcu_idx = srcu_read_lock(&remove_cache_srcu); | |
026d1eaf | 246 | raw_spin_lock_irqsave(&quarantine_lock, flags); |
55834c59 AP |
247 | |
248 | /* | |
249 | * Update quarantine size in case of hotplug. Allocate a fraction of | |
250 | * the installed memory to quarantine minus per-cpu queue limits. | |
251 | */ | |
ca79b0c2 | 252 | total_size = (totalram_pages() << PAGE_SHIFT) / |
55834c59 | 253 | QUARANTINE_FRACTION; |
c3cee372 | 254 | percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus(); |
64abdcb2 DV |
255 | new_quarantine_size = (total_size < percpu_quarantines) ? |
256 | 0 : total_size - percpu_quarantines; | |
257 | WRITE_ONCE(quarantine_max_size, new_quarantine_size); | |
258 | /* Aim at consuming at most 1/2 of slots in quarantine. */ | |
259 | WRITE_ONCE(quarantine_batch_size, max((size_t)QUARANTINE_PERCPU_SIZE, | |
260 | 2 * total_size / QUARANTINE_BATCHES)); | |
261 | ||
262 | if (likely(quarantine_size > quarantine_max_size)) { | |
263 | qlist_move_all(&global_quarantine[quarantine_head], &to_free); | |
264 | WRITE_ONCE(quarantine_size, quarantine_size - to_free.bytes); | |
265 | quarantine_head++; | |
266 | if (quarantine_head == QUARANTINE_BATCHES) | |
267 | quarantine_head = 0; | |
55834c59 | 268 | } |
55834c59 | 269 | |
026d1eaf | 270 | raw_spin_unlock_irqrestore(&quarantine_lock, flags); |
55834c59 AP |
271 | |
272 | qlist_free_all(&to_free, NULL); | |
ce5bec54 | 273 | srcu_read_unlock(&remove_cache_srcu, srcu_idx); |
55834c59 AP |
274 | } |
275 | ||
276 | static void qlist_move_cache(struct qlist_head *from, | |
277 | struct qlist_head *to, | |
278 | struct kmem_cache *cache) | |
279 | { | |
0ab686d8 | 280 | struct qlist_node *curr; |
55834c59 AP |
281 | |
282 | if (unlikely(qlist_empty(from))) | |
283 | return; | |
284 | ||
285 | curr = from->head; | |
0ab686d8 | 286 | qlist_init(from); |
55834c59 | 287 | while (curr) { |
0ab686d8 JK |
288 | struct qlist_node *next = curr->next; |
289 | struct kmem_cache *obj_cache = qlink_to_cache(curr); | |
290 | ||
291 | if (obj_cache == cache) | |
292 | qlist_put(to, curr, obj_cache->size); | |
293 | else | |
294 | qlist_put(from, curr, obj_cache->size); | |
295 | ||
296 | curr = next; | |
55834c59 AP |
297 | } |
298 | } | |
299 | ||
300 | static void per_cpu_remove_cache(void *arg) | |
301 | { | |
302 | struct kmem_cache *cache = arg; | |
303 | struct qlist_head to_free = QLIST_INIT; | |
304 | struct qlist_head *q; | |
305 | ||
306 | q = this_cpu_ptr(&cpu_quarantine); | |
307 | qlist_move_cache(q, &to_free, cache); | |
308 | qlist_free_all(&to_free, cache); | |
309 | } | |
310 | ||
f9fa1d91 | 311 | /* Free all quarantined objects belonging to cache. */ |
55834c59 AP |
312 | void quarantine_remove_cache(struct kmem_cache *cache) |
313 | { | |
64abdcb2 | 314 | unsigned long flags, i; |
55834c59 AP |
315 | struct qlist_head to_free = QLIST_INIT; |
316 | ||
ce5bec54 DV |
317 | /* |
318 | * Must be careful to not miss any objects that are being moved from | |
319 | * per-cpu list to the global quarantine in quarantine_put(), | |
320 | * nor objects being freed in quarantine_reduce(). on_each_cpu() | |
321 | * achieves the first goal, while synchronize_srcu() achieves the | |
322 | * second. | |
323 | */ | |
55834c59 AP |
324 | on_each_cpu(per_cpu_remove_cache, cache, 1); |
325 | ||
026d1eaf | 326 | raw_spin_lock_irqsave(&quarantine_lock, flags); |
68fd814a DV |
327 | for (i = 0; i < QUARANTINE_BATCHES; i++) { |
328 | if (qlist_empty(&global_quarantine[i])) | |
329 | continue; | |
64abdcb2 | 330 | qlist_move_cache(&global_quarantine[i], &to_free, cache); |
68fd814a | 331 | /* Scanning whole quarantine can take a while. */ |
026d1eaf | 332 | raw_spin_unlock_irqrestore(&quarantine_lock, flags); |
68fd814a | 333 | cond_resched(); |
026d1eaf | 334 | raw_spin_lock_irqsave(&quarantine_lock, flags); |
68fd814a | 335 | } |
026d1eaf | 336 | raw_spin_unlock_irqrestore(&quarantine_lock, flags); |
55834c59 AP |
337 | |
338 | qlist_free_all(&to_free, cache); | |
ce5bec54 DV |
339 | |
340 | synchronize_srcu(&remove_cache_srcu); | |
55834c59 | 341 | } |
6c82d45c KYL |
342 | |
343 | static int kasan_cpu_online(unsigned int cpu) | |
344 | { | |
345 | this_cpu_ptr(&cpu_quarantine)->offline = false; | |
346 | return 0; | |
347 | } | |
348 | ||
349 | static int kasan_cpu_offline(unsigned int cpu) | |
350 | { | |
351 | struct qlist_head *q; | |
352 | ||
353 | q = this_cpu_ptr(&cpu_quarantine); | |
354 | /* Ensure the ordering between the writing to q->offline and | |
355 | * qlist_free_all. Otherwise, cpu_quarantine may be corrupted | |
356 | * by interrupt. | |
357 | */ | |
358 | WRITE_ONCE(q->offline, true); | |
359 | barrier(); | |
360 | qlist_free_all(q, NULL); | |
361 | return 0; | |
362 | } | |
363 | ||
364 | static int __init kasan_cpu_quarantine_init(void) | |
365 | { | |
366 | int ret = 0; | |
367 | ||
368 | ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/kasan:online", | |
369 | kasan_cpu_online, kasan_cpu_offline); | |
370 | if (ret < 0) | |
371 | pr_err("kasan cpu quarantine register failed [%d]\n", ret); | |
372 | return ret; | |
373 | } | |
374 | late_initcall(kasan_cpu_quarantine_init); |