Merge tag 'mmc-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc
[linux-2.6-microblaze.git] / mm / kasan / quarantine.c
1 // SPDX-License-Identifier: GPL-2.0
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.
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>
19 #include <linux/srcu.h>
20 #include <linux/string.h>
21 #include <linux/types.h>
22 #include <linux/cpuhotplug.h>
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 single-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;
37         bool offline;
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
83 #define QUARANTINE_PERCPU_SIZE (1 << 20)
84 #define QUARANTINE_BATCHES \
85         (1024 > 4 * CONFIG_NR_CPUS ? 1024 : 4 * CONFIG_NR_CPUS)
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
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;
99 static DEFINE_RAW_SPINLOCK(quarantine_lock);
100 DEFINE_STATIC_SRCU(remove_cache_srcu);
101
102 /* Maximum size of the global queue. */
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;
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
118 static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink)
119 {
120         return virt_to_slab(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);
135         struct kasan_free_meta *meta = kasan_get_free_meta(cache, object);
136         unsigned long flags;
137
138         if (IS_ENABLED(CONFIG_SLAB))
139                 local_irq_save(flags);
140
141         /*
142          * If init_on_free is enabled and KASAN's free metadata is stored in
143          * the object, zero the metadata. Otherwise, the object's memory will
144          * not be properly zeroed, as KASAN saves the metadata after the slab
145          * allocator zeroes the object.
146          */
147         if (slab_want_init_on_free(cache) &&
148             cache->kasan_info.free_meta_offset == 0)
149                 memzero_explicit(meta, sizeof(*meta));
150
151         /*
152          * As the object now gets freed from the quarantine, assume that its
153          * free track is no longer valid.
154          */
155         *(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREE;
156
157         ___cache_free(cache, object, _THIS_IP_);
158
159         if (IS_ENABLED(CONFIG_SLAB))
160                 local_irq_restore(flags);
161 }
162
163 static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache)
164 {
165         struct qlist_node *qlink;
166
167         if (unlikely(qlist_empty(q)))
168                 return;
169
170         qlink = q->head;
171         while (qlink) {
172                 struct kmem_cache *obj_cache =
173                         cache ? cache : qlink_to_cache(qlink);
174                 struct qlist_node *next = qlink->next;
175
176                 qlink_free(qlink, obj_cache);
177                 qlink = next;
178         }
179         qlist_init(q);
180 }
181
182 bool kasan_quarantine_put(struct kmem_cache *cache, void *object)
183 {
184         unsigned long flags;
185         struct qlist_head *q;
186         struct qlist_head temp = QLIST_INIT;
187         struct kasan_free_meta *meta = kasan_get_free_meta(cache, object);
188
189         /*
190          * If there's no metadata for this object, don't put it into
191          * quarantine.
192          */
193         if (!meta)
194                 return false;
195
196         /*
197          * Note: irq must be disabled until after we move the batch to the
198          * global quarantine. Otherwise kasan_quarantine_remove_cache() can
199          * miss some objects belonging to the cache if they are in our local
200          * temp list. kasan_quarantine_remove_cache() executes on_each_cpu()
201          * at the beginning which ensures that it either sees the objects in
202          * per-cpu lists or in the global quarantine.
203          */
204         local_irq_save(flags);
205
206         q = this_cpu_ptr(&cpu_quarantine);
207         if (q->offline) {
208                 local_irq_restore(flags);
209                 return false;
210         }
211         qlist_put(q, &meta->quarantine_link, cache->size);
212         if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
213                 qlist_move_all(q, &temp);
214
215                 raw_spin_lock(&quarantine_lock);
216                 WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes);
217                 qlist_move_all(&temp, &global_quarantine[quarantine_tail]);
218                 if (global_quarantine[quarantine_tail].bytes >=
219                                 READ_ONCE(quarantine_batch_size)) {
220                         int new_tail;
221
222                         new_tail = quarantine_tail + 1;
223                         if (new_tail == QUARANTINE_BATCHES)
224                                 new_tail = 0;
225                         if (new_tail != quarantine_head)
226                                 quarantine_tail = new_tail;
227                 }
228                 raw_spin_unlock(&quarantine_lock);
229         }
230
231         local_irq_restore(flags);
232
233         return true;
234 }
235
236 void kasan_quarantine_reduce(void)
237 {
238         size_t total_size, new_quarantine_size, percpu_quarantines;
239         unsigned long flags;
240         int srcu_idx;
241         struct qlist_head to_free = QLIST_INIT;
242
243         if (likely(READ_ONCE(quarantine_size) <=
244                    READ_ONCE(quarantine_max_size)))
245                 return;
246
247         /*
248          * srcu critical section ensures that kasan_quarantine_remove_cache()
249          * will not miss objects belonging to the cache while they are in our
250          * local to_free list. srcu is chosen because (1) it gives us private
251          * grace period domain that does not interfere with anything else,
252          * and (2) it allows synchronize_srcu() to return without waiting
253          * if there are no pending read critical sections (which is the
254          * expected case).
255          */
256         srcu_idx = srcu_read_lock(&remove_cache_srcu);
257         raw_spin_lock_irqsave(&quarantine_lock, flags);
258
259         /*
260          * Update quarantine size in case of hotplug. Allocate a fraction of
261          * the installed memory to quarantine minus per-cpu queue limits.
262          */
263         total_size = (totalram_pages() << PAGE_SHIFT) /
264                 QUARANTINE_FRACTION;
265         percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus();
266         new_quarantine_size = (total_size < percpu_quarantines) ?
267                 0 : total_size - percpu_quarantines;
268         WRITE_ONCE(quarantine_max_size, new_quarantine_size);
269         /* Aim at consuming at most 1/2 of slots in quarantine. */
270         WRITE_ONCE(quarantine_batch_size, max((size_t)QUARANTINE_PERCPU_SIZE,
271                 2 * total_size / QUARANTINE_BATCHES));
272
273         if (likely(quarantine_size > quarantine_max_size)) {
274                 qlist_move_all(&global_quarantine[quarantine_head], &to_free);
275                 WRITE_ONCE(quarantine_size, quarantine_size - to_free.bytes);
276                 quarantine_head++;
277                 if (quarantine_head == QUARANTINE_BATCHES)
278                         quarantine_head = 0;
279         }
280
281         raw_spin_unlock_irqrestore(&quarantine_lock, flags);
282
283         qlist_free_all(&to_free, NULL);
284         srcu_read_unlock(&remove_cache_srcu, srcu_idx);
285 }
286
287 static void qlist_move_cache(struct qlist_head *from,
288                                    struct qlist_head *to,
289                                    struct kmem_cache *cache)
290 {
291         struct qlist_node *curr;
292
293         if (unlikely(qlist_empty(from)))
294                 return;
295
296         curr = from->head;
297         qlist_init(from);
298         while (curr) {
299                 struct qlist_node *next = curr->next;
300                 struct kmem_cache *obj_cache = qlink_to_cache(curr);
301
302                 if (obj_cache == cache)
303                         qlist_put(to, curr, obj_cache->size);
304                 else
305                         qlist_put(from, curr, obj_cache->size);
306
307                 curr = next;
308         }
309 }
310
311 static void per_cpu_remove_cache(void *arg)
312 {
313         struct kmem_cache *cache = arg;
314         struct qlist_head to_free = QLIST_INIT;
315         struct qlist_head *q;
316
317         q = this_cpu_ptr(&cpu_quarantine);
318         qlist_move_cache(q, &to_free, cache);
319         qlist_free_all(&to_free, cache);
320 }
321
322 /* Free all quarantined objects belonging to cache. */
323 void kasan_quarantine_remove_cache(struct kmem_cache *cache)
324 {
325         unsigned long flags, i;
326         struct qlist_head to_free = QLIST_INIT;
327
328         /*
329          * Must be careful to not miss any objects that are being moved from
330          * per-cpu list to the global quarantine in kasan_quarantine_put(),
331          * nor objects being freed in kasan_quarantine_reduce(). on_each_cpu()
332          * achieves the first goal, while synchronize_srcu() achieves the
333          * second.
334          */
335         on_each_cpu(per_cpu_remove_cache, cache, 1);
336
337         raw_spin_lock_irqsave(&quarantine_lock, flags);
338         for (i = 0; i < QUARANTINE_BATCHES; i++) {
339                 if (qlist_empty(&global_quarantine[i]))
340                         continue;
341                 qlist_move_cache(&global_quarantine[i], &to_free, cache);
342                 /* Scanning whole quarantine can take a while. */
343                 raw_spin_unlock_irqrestore(&quarantine_lock, flags);
344                 cond_resched();
345                 raw_spin_lock_irqsave(&quarantine_lock, flags);
346         }
347         raw_spin_unlock_irqrestore(&quarantine_lock, flags);
348
349         qlist_free_all(&to_free, cache);
350
351         synchronize_srcu(&remove_cache_srcu);
352 }
353
354 static int kasan_cpu_online(unsigned int cpu)
355 {
356         this_cpu_ptr(&cpu_quarantine)->offline = false;
357         return 0;
358 }
359
360 static int kasan_cpu_offline(unsigned int cpu)
361 {
362         struct qlist_head *q;
363
364         q = this_cpu_ptr(&cpu_quarantine);
365         /* Ensure the ordering between the writing to q->offline and
366          * qlist_free_all. Otherwise, cpu_quarantine may be corrupted
367          * by interrupt.
368          */
369         WRITE_ONCE(q->offline, true);
370         barrier();
371         qlist_free_all(q, NULL);
372         return 0;
373 }
374
375 static int __init kasan_cpu_quarantine_init(void)
376 {
377         int ret = 0;
378
379         ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/kasan:online",
380                                 kasan_cpu_online, kasan_cpu_offline);
381         if (ret < 0)
382                 pr_err("kasan cpu quarantine register failed [%d]\n", ret);
383         return ret;
384 }
385 late_initcall(kasan_cpu_quarantine_init);