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162          * free track is no longer valid.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