Commit | Line | Data |
---|---|---|
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 | /* | |
f0953a1b | 30 | * Each queue is a single-linked list, which also stores the total size of |
55834c59 AP |
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 | 101 | |
07d067e4 Z |
102 | #ifdef CONFIG_PREEMPT_RT |
103 | struct cpu_shrink_qlist { | |
104 | raw_spinlock_t lock; | |
105 | struct qlist_head qlist; | |
106 | }; | |
107 | ||
108 | static DEFINE_PER_CPU(struct cpu_shrink_qlist, shrink_qlist) = { | |
109 | .lock = __RAW_SPIN_LOCK_UNLOCKED(shrink_qlist.lock), | |
110 | }; | |
111 | #endif | |
112 | ||
55834c59 | 113 | /* Maximum size of the global queue. */ |
64abdcb2 DV |
114 | static unsigned long quarantine_max_size; |
115 | ||
116 | /* | |
117 | * Target size of a batch in global_quarantine. | |
118 | * Usually equal to QUARANTINE_PERCPU_SIZE unless we have too much RAM. | |
119 | */ | |
120 | static unsigned long quarantine_batch_size; | |
55834c59 AP |
121 | |
122 | /* | |
123 | * The fraction of physical memory the quarantine is allowed to occupy. | |
124 | * Quarantine doesn't support memory shrinker with SLAB allocator, so we keep | |
125 | * the ratio low to avoid OOM. | |
126 | */ | |
127 | #define QUARANTINE_FRACTION 32 | |
128 | ||
55834c59 AP |
129 | static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink) |
130 | { | |
6e48a966 | 131 | return virt_to_slab(qlink)->slab_cache; |
55834c59 AP |
132 | } |
133 | ||
134 | static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache) | |
135 | { | |
136 | struct kasan_free_meta *free_info = | |
137 | container_of(qlink, struct kasan_free_meta, | |
138 | quarantine_link); | |
139 | ||
140 | return ((void *)free_info) - cache->kasan_info.free_meta_offset; | |
141 | } | |
142 | ||
143 | static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache) | |
144 | { | |
145 | void *object = qlink_to_object(qlink, cache); | |
26dca996 | 146 | struct kasan_free_meta *meta = kasan_get_free_meta(cache, object); |
55834c59 AP |
147 | unsigned long flags; |
148 | ||
f7376aed AR |
149 | if (IS_ENABLED(CONFIG_SLAB)) |
150 | local_irq_save(flags); | |
151 | ||
26dca996 AK |
152 | /* |
153 | * If init_on_free is enabled and KASAN's free metadata is stored in | |
154 | * the object, zero the metadata. Otherwise, the object's memory will | |
155 | * not be properly zeroed, as KASAN saves the metadata after the slab | |
156 | * allocator zeroes the object. | |
157 | */ | |
158 | if (slab_want_init_on_free(cache) && | |
159 | cache->kasan_info.free_meta_offset == 0) | |
160 | memzero_explicit(meta, sizeof(*meta)); | |
161 | ||
97593cad | 162 | /* |
f0953a1b | 163 | * As the object now gets freed from the quarantine, assume that its |
97593cad AK |
164 | * free track is no longer valid. |
165 | */ | |
06bc4cf6 | 166 | *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE; |
97593cad | 167 | |
55834c59 | 168 | ___cache_free(cache, object, _THIS_IP_); |
f7376aed AR |
169 | |
170 | if (IS_ENABLED(CONFIG_SLAB)) | |
171 | local_irq_restore(flags); | |
55834c59 AP |
172 | } |
173 | ||
174 | static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache) | |
175 | { | |
176 | struct qlist_node *qlink; | |
177 | ||
178 | if (unlikely(qlist_empty(q))) | |
179 | return; | |
180 | ||
181 | qlink = q->head; | |
182 | while (qlink) { | |
183 | struct kmem_cache *obj_cache = | |
184 | cache ? cache : qlink_to_cache(qlink); | |
185 | struct qlist_node *next = qlink->next; | |
186 | ||
187 | qlink_free(qlink, obj_cache); | |
188 | qlink = next; | |
189 | } | |
190 | qlist_init(q); | |
191 | } | |
192 | ||
f00748bf | 193 | bool kasan_quarantine_put(struct kmem_cache *cache, void *object) |
55834c59 AP |
194 | { |
195 | unsigned long flags; | |
196 | struct qlist_head *q; | |
197 | struct qlist_head temp = QLIST_INIT; | |
6476792f | 198 | struct kasan_free_meta *meta = kasan_get_free_meta(cache, object); |
55834c59 | 199 | |
97593cad AK |
200 | /* |
201 | * If there's no metadata for this object, don't put it into | |
202 | * quarantine. | |
203 | */ | |
204 | if (!meta) | |
205 | return false; | |
206 | ||
ce5bec54 DV |
207 | /* |
208 | * Note: irq must be disabled until after we move the batch to the | |
f00748bf AK |
209 | * global quarantine. Otherwise kasan_quarantine_remove_cache() can |
210 | * miss some objects belonging to the cache if they are in our local | |
211 | * temp list. kasan_quarantine_remove_cache() executes on_each_cpu() | |
212 | * at the beginning which ensures that it either sees the objects in | |
213 | * per-cpu lists or in the global quarantine. | |
ce5bec54 | 214 | */ |
55834c59 AP |
215 | local_irq_save(flags); |
216 | ||
217 | q = this_cpu_ptr(&cpu_quarantine); | |
6c82d45c KYL |
218 | if (q->offline) { |
219 | local_irq_restore(flags); | |
97593cad | 220 | return false; |
6c82d45c | 221 | } |
6476792f | 222 | qlist_put(q, &meta->quarantine_link, cache->size); |
ce5bec54 | 223 | if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) { |
55834c59 AP |
224 | qlist_move_all(q, &temp); |
225 | ||
026d1eaf | 226 | raw_spin_lock(&quarantine_lock); |
64abdcb2 DV |
227 | WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes); |
228 | qlist_move_all(&temp, &global_quarantine[quarantine_tail]); | |
229 | if (global_quarantine[quarantine_tail].bytes >= | |
230 | READ_ONCE(quarantine_batch_size)) { | |
231 | int new_tail; | |
232 | ||
233 | new_tail = quarantine_tail + 1; | |
234 | if (new_tail == QUARANTINE_BATCHES) | |
235 | new_tail = 0; | |
236 | if (new_tail != quarantine_head) | |
237 | quarantine_tail = new_tail; | |
238 | } | |
026d1eaf | 239 | raw_spin_unlock(&quarantine_lock); |
55834c59 | 240 | } |
ce5bec54 DV |
241 | |
242 | local_irq_restore(flags); | |
97593cad AK |
243 | |
244 | return true; | |
55834c59 AP |
245 | } |
246 | ||
f00748bf | 247 | void kasan_quarantine_reduce(void) |
55834c59 | 248 | { |
64abdcb2 | 249 | size_t total_size, new_quarantine_size, percpu_quarantines; |
55834c59 | 250 | unsigned long flags; |
ce5bec54 | 251 | int srcu_idx; |
55834c59 | 252 | struct qlist_head to_free = QLIST_INIT; |
55834c59 | 253 | |
64abdcb2 DV |
254 | if (likely(READ_ONCE(quarantine_size) <= |
255 | READ_ONCE(quarantine_max_size))) | |
55834c59 AP |
256 | return; |
257 | ||
ce5bec54 | 258 | /* |
f00748bf | 259 | * srcu critical section ensures that kasan_quarantine_remove_cache() |
ce5bec54 DV |
260 | * will not miss objects belonging to the cache while they are in our |
261 | * local to_free list. srcu is chosen because (1) it gives us private | |
262 | * grace period domain that does not interfere with anything else, | |
263 | * and (2) it allows synchronize_srcu() to return without waiting | |
264 | * if there are no pending read critical sections (which is the | |
265 | * expected case). | |
266 | */ | |
267 | srcu_idx = srcu_read_lock(&remove_cache_srcu); | |
026d1eaf | 268 | raw_spin_lock_irqsave(&quarantine_lock, flags); |
55834c59 AP |
269 | |
270 | /* | |
271 | * Update quarantine size in case of hotplug. Allocate a fraction of | |
272 | * the installed memory to quarantine minus per-cpu queue limits. | |
273 | */ | |
ca79b0c2 | 274 | total_size = (totalram_pages() << PAGE_SHIFT) / |
55834c59 | 275 | QUARANTINE_FRACTION; |
c3cee372 | 276 | percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus(); |
64abdcb2 DV |
277 | new_quarantine_size = (total_size < percpu_quarantines) ? |
278 | 0 : total_size - percpu_quarantines; | |
279 | WRITE_ONCE(quarantine_max_size, new_quarantine_size); | |
280 | /* Aim at consuming at most 1/2 of slots in quarantine. */ | |
281 | WRITE_ONCE(quarantine_batch_size, max((size_t)QUARANTINE_PERCPU_SIZE, | |
282 | 2 * total_size / QUARANTINE_BATCHES)); | |
283 | ||
284 | if (likely(quarantine_size > quarantine_max_size)) { | |
285 | qlist_move_all(&global_quarantine[quarantine_head], &to_free); | |
286 | WRITE_ONCE(quarantine_size, quarantine_size - to_free.bytes); | |
287 | quarantine_head++; | |
288 | if (quarantine_head == QUARANTINE_BATCHES) | |
289 | quarantine_head = 0; | |
55834c59 | 290 | } |
55834c59 | 291 | |
026d1eaf | 292 | raw_spin_unlock_irqrestore(&quarantine_lock, flags); |
55834c59 AP |
293 | |
294 | qlist_free_all(&to_free, NULL); | |
ce5bec54 | 295 | srcu_read_unlock(&remove_cache_srcu, srcu_idx); |
55834c59 AP |
296 | } |
297 | ||
298 | static void qlist_move_cache(struct qlist_head *from, | |
299 | struct qlist_head *to, | |
300 | struct kmem_cache *cache) | |
301 | { | |
0ab686d8 | 302 | struct qlist_node *curr; |
55834c59 AP |
303 | |
304 | if (unlikely(qlist_empty(from))) | |
305 | return; | |
306 | ||
307 | curr = from->head; | |
0ab686d8 | 308 | qlist_init(from); |
55834c59 | 309 | while (curr) { |
0ab686d8 JK |
310 | struct qlist_node *next = curr->next; |
311 | struct kmem_cache *obj_cache = qlink_to_cache(curr); | |
312 | ||
313 | if (obj_cache == cache) | |
314 | qlist_put(to, curr, obj_cache->size); | |
315 | else | |
316 | qlist_put(from, curr, obj_cache->size); | |
317 | ||
318 | curr = next; | |
55834c59 AP |
319 | } |
320 | } | |
321 | ||
07d067e4 Z |
322 | #ifndef CONFIG_PREEMPT_RT |
323 | static void __per_cpu_remove_cache(struct qlist_head *q, void *arg) | |
55834c59 AP |
324 | { |
325 | struct kmem_cache *cache = arg; | |
326 | struct qlist_head to_free = QLIST_INIT; | |
07d067e4 Z |
327 | |
328 | qlist_move_cache(q, &to_free, cache); | |
329 | qlist_free_all(&to_free, cache); | |
330 | } | |
331 | #else | |
332 | static void __per_cpu_remove_cache(struct qlist_head *q, void *arg) | |
333 | { | |
334 | struct kmem_cache *cache = arg; | |
335 | unsigned long flags; | |
336 | struct cpu_shrink_qlist *sq; | |
337 | ||
338 | sq = this_cpu_ptr(&shrink_qlist); | |
339 | raw_spin_lock_irqsave(&sq->lock, flags); | |
340 | qlist_move_cache(q, &sq->qlist, cache); | |
341 | raw_spin_unlock_irqrestore(&sq->lock, flags); | |
342 | } | |
343 | #endif | |
344 | ||
345 | static void per_cpu_remove_cache(void *arg) | |
346 | { | |
55834c59 AP |
347 | struct qlist_head *q; |
348 | ||
349 | q = this_cpu_ptr(&cpu_quarantine); | |
31fa985b Z |
350 | /* |
351 | * Ensure the ordering between the writing to q->offline and | |
352 | * per_cpu_remove_cache. Prevent cpu_quarantine from being corrupted | |
353 | * by interrupt. | |
354 | */ | |
355 | if (READ_ONCE(q->offline)) | |
356 | return; | |
07d067e4 | 357 | __per_cpu_remove_cache(q, arg); |
55834c59 AP |
358 | } |
359 | ||
f9fa1d91 | 360 | /* Free all quarantined objects belonging to cache. */ |
f00748bf | 361 | void kasan_quarantine_remove_cache(struct kmem_cache *cache) |
55834c59 | 362 | { |
64abdcb2 | 363 | unsigned long flags, i; |
55834c59 AP |
364 | struct qlist_head to_free = QLIST_INIT; |
365 | ||
ce5bec54 DV |
366 | /* |
367 | * Must be careful to not miss any objects that are being moved from | |
f00748bf AK |
368 | * per-cpu list to the global quarantine in kasan_quarantine_put(), |
369 | * nor objects being freed in kasan_quarantine_reduce(). on_each_cpu() | |
ce5bec54 DV |
370 | * achieves the first goal, while synchronize_srcu() achieves the |
371 | * second. | |
372 | */ | |
55834c59 AP |
373 | on_each_cpu(per_cpu_remove_cache, cache, 1); |
374 | ||
07d067e4 Z |
375 | #ifdef CONFIG_PREEMPT_RT |
376 | { | |
377 | int cpu; | |
378 | struct cpu_shrink_qlist *sq; | |
379 | ||
380 | for_each_online_cpu(cpu) { | |
381 | sq = per_cpu_ptr(&shrink_qlist, cpu); | |
382 | raw_spin_lock_irqsave(&sq->lock, flags); | |
383 | qlist_move_cache(&sq->qlist, &to_free, cache); | |
384 | raw_spin_unlock_irqrestore(&sq->lock, flags); | |
385 | } | |
386 | qlist_free_all(&to_free, cache); | |
387 | } | |
388 | #endif | |
389 | ||
026d1eaf | 390 | raw_spin_lock_irqsave(&quarantine_lock, flags); |
68fd814a DV |
391 | for (i = 0; i < QUARANTINE_BATCHES; i++) { |
392 | if (qlist_empty(&global_quarantine[i])) | |
393 | continue; | |
64abdcb2 | 394 | qlist_move_cache(&global_quarantine[i], &to_free, cache); |
68fd814a | 395 | /* Scanning whole quarantine can take a while. */ |
026d1eaf | 396 | raw_spin_unlock_irqrestore(&quarantine_lock, flags); |
68fd814a | 397 | cond_resched(); |
026d1eaf | 398 | raw_spin_lock_irqsave(&quarantine_lock, flags); |
68fd814a | 399 | } |
026d1eaf | 400 | raw_spin_unlock_irqrestore(&quarantine_lock, flags); |
55834c59 AP |
401 | |
402 | qlist_free_all(&to_free, cache); | |
ce5bec54 DV |
403 | |
404 | synchronize_srcu(&remove_cache_srcu); | |
55834c59 | 405 | } |
6c82d45c KYL |
406 | |
407 | static int kasan_cpu_online(unsigned int cpu) | |
408 | { | |
409 | this_cpu_ptr(&cpu_quarantine)->offline = false; | |
410 | return 0; | |
411 | } | |
412 | ||
413 | static int kasan_cpu_offline(unsigned int cpu) | |
414 | { | |
415 | struct qlist_head *q; | |
416 | ||
417 | q = this_cpu_ptr(&cpu_quarantine); | |
418 | /* Ensure the ordering between the writing to q->offline and | |
419 | * qlist_free_all. Otherwise, cpu_quarantine may be corrupted | |
420 | * by interrupt. | |
421 | */ | |
422 | WRITE_ONCE(q->offline, true); | |
423 | barrier(); | |
424 | qlist_free_all(q, NULL); | |
425 | return 0; | |
426 | } | |
427 | ||
428 | static int __init kasan_cpu_quarantine_init(void) | |
429 | { | |
430 | int ret = 0; | |
431 | ||
432 | ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/kasan:online", | |
433 | kasan_cpu_online, kasan_cpu_offline); | |
434 | if (ret < 0) | |
435 | pr_err("kasan cpu quarantine register failed [%d]\n", ret); | |
436 | return ret; | |
437 | } | |
438 | late_initcall(kasan_cpu_quarantine_init); |