xref: /openbmc/linux/mm/kasan/quarantine.c (revision 4f205687)
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>
28 #include <linux/string.h>
29 #include <linux/types.h>
30 
31 #include "../slab.h"
32 #include "kasan.h"
33 
34 /* Data structure and operations for quarantine queues. */
35 
36 /*
37  * Each queue is a signle-linked list, which also stores the total size of
38  * objects inside of it.
39  */
40 struct qlist_head {
41 	struct qlist_node *head;
42 	struct qlist_node *tail;
43 	size_t bytes;
44 };
45 
46 #define QLIST_INIT { NULL, NULL, 0 }
47 
48 static bool qlist_empty(struct qlist_head *q)
49 {
50 	return !q->head;
51 }
52 
53 static void qlist_init(struct qlist_head *q)
54 {
55 	q->head = q->tail = NULL;
56 	q->bytes = 0;
57 }
58 
59 static void qlist_put(struct qlist_head *q, struct qlist_node *qlink,
60 		size_t size)
61 {
62 	if (unlikely(qlist_empty(q)))
63 		q->head = qlink;
64 	else
65 		q->tail->next = qlink;
66 	q->tail = qlink;
67 	qlink->next = NULL;
68 	q->bytes += size;
69 }
70 
71 static void qlist_move_all(struct qlist_head *from, struct qlist_head *to)
72 {
73 	if (unlikely(qlist_empty(from)))
74 		return;
75 
76 	if (qlist_empty(to)) {
77 		*to = *from;
78 		qlist_init(from);
79 		return;
80 	}
81 
82 	to->tail->next = from->head;
83 	to->tail = from->tail;
84 	to->bytes += from->bytes;
85 
86 	qlist_init(from);
87 }
88 
89 static void qlist_move(struct qlist_head *from, struct qlist_node *last,
90 		struct qlist_head *to, size_t size)
91 {
92 	if (unlikely(last == from->tail)) {
93 		qlist_move_all(from, to);
94 		return;
95 	}
96 	if (qlist_empty(to))
97 		to->head = from->head;
98 	else
99 		to->tail->next = from->head;
100 	to->tail = last;
101 	from->head = last->next;
102 	last->next = NULL;
103 	from->bytes -= size;
104 	to->bytes += size;
105 }
106 
107 
108 /*
109  * The object quarantine consists of per-cpu queues and a global queue,
110  * guarded by quarantine_lock.
111  */
112 static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine);
113 
114 static struct qlist_head global_quarantine;
115 static DEFINE_SPINLOCK(quarantine_lock);
116 
117 /* Maximum size of the global queue. */
118 static unsigned long quarantine_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 #define QUARANTINE_LOW_SIZE (READ_ONCE(quarantine_size) * 3 / 4)
128 #define QUARANTINE_PERCPU_SIZE (1 << 20)
129 
130 static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink)
131 {
132 	return virt_to_head_page(qlink)->slab_cache;
133 }
134 
135 static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache)
136 {
137 	struct kasan_free_meta *free_info =
138 		container_of(qlink, struct kasan_free_meta,
139 			     quarantine_link);
140 
141 	return ((void *)free_info) - cache->kasan_info.free_meta_offset;
142 }
143 
144 static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
145 {
146 	void *object = qlink_to_object(qlink, cache);
147 	struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
148 	unsigned long flags;
149 
150 	local_irq_save(flags);
151 	alloc_info->state = KASAN_STATE_FREE;
152 	___cache_free(cache, object, _THIS_IP_);
153 	local_irq_restore(flags);
154 }
155 
156 static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache)
157 {
158 	struct qlist_node *qlink;
159 
160 	if (unlikely(qlist_empty(q)))
161 		return;
162 
163 	qlink = q->head;
164 	while (qlink) {
165 		struct kmem_cache *obj_cache =
166 			cache ? cache :	qlink_to_cache(qlink);
167 		struct qlist_node *next = qlink->next;
168 
169 		qlink_free(qlink, obj_cache);
170 		qlink = next;
171 	}
172 	qlist_init(q);
173 }
174 
175 void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
176 {
177 	unsigned long flags;
178 	struct qlist_head *q;
179 	struct qlist_head temp = QLIST_INIT;
180 
181 	local_irq_save(flags);
182 
183 	q = this_cpu_ptr(&cpu_quarantine);
184 	qlist_put(q, &info->quarantine_link, cache->size);
185 	if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE))
186 		qlist_move_all(q, &temp);
187 
188 	local_irq_restore(flags);
189 
190 	if (unlikely(!qlist_empty(&temp))) {
191 		spin_lock_irqsave(&quarantine_lock, flags);
192 		qlist_move_all(&temp, &global_quarantine);
193 		spin_unlock_irqrestore(&quarantine_lock, flags);
194 	}
195 }
196 
197 void quarantine_reduce(void)
198 {
199 	size_t new_quarantine_size;
200 	unsigned long flags;
201 	struct qlist_head to_free = QLIST_INIT;
202 	size_t size_to_free = 0;
203 	struct qlist_node *last;
204 
205 	if (likely(READ_ONCE(global_quarantine.bytes) <=
206 		   READ_ONCE(quarantine_size)))
207 		return;
208 
209 	spin_lock_irqsave(&quarantine_lock, flags);
210 
211 	/*
212 	 * Update quarantine size in case of hotplug. Allocate a fraction of
213 	 * the installed memory to quarantine minus per-cpu queue limits.
214 	 */
215 	new_quarantine_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) /
216 		QUARANTINE_FRACTION;
217 	new_quarantine_size -= QUARANTINE_PERCPU_SIZE * num_online_cpus();
218 	WRITE_ONCE(quarantine_size, new_quarantine_size);
219 
220 	last = global_quarantine.head;
221 	while (last) {
222 		struct kmem_cache *cache = qlink_to_cache(last);
223 
224 		size_to_free += cache->size;
225 		if (!last->next || size_to_free >
226 		    global_quarantine.bytes - QUARANTINE_LOW_SIZE)
227 			break;
228 		last = last->next;
229 	}
230 	qlist_move(&global_quarantine, last, &to_free, size_to_free);
231 
232 	spin_unlock_irqrestore(&quarantine_lock, flags);
233 
234 	qlist_free_all(&to_free, NULL);
235 }
236 
237 static void qlist_move_cache(struct qlist_head *from,
238 				   struct qlist_head *to,
239 				   struct kmem_cache *cache)
240 {
241 	struct qlist_node *curr;
242 
243 	if (unlikely(qlist_empty(from)))
244 		return;
245 
246 	curr = from->head;
247 	qlist_init(from);
248 	while (curr) {
249 		struct qlist_node *next = curr->next;
250 		struct kmem_cache *obj_cache = qlink_to_cache(curr);
251 
252 		if (obj_cache == cache)
253 			qlist_put(to, curr, obj_cache->size);
254 		else
255 			qlist_put(from, curr, obj_cache->size);
256 
257 		curr = next;
258 	}
259 }
260 
261 static void per_cpu_remove_cache(void *arg)
262 {
263 	struct kmem_cache *cache = arg;
264 	struct qlist_head to_free = QLIST_INIT;
265 	struct qlist_head *q;
266 
267 	q = this_cpu_ptr(&cpu_quarantine);
268 	qlist_move_cache(q, &to_free, cache);
269 	qlist_free_all(&to_free, cache);
270 }
271 
272 void quarantine_remove_cache(struct kmem_cache *cache)
273 {
274 	unsigned long flags;
275 	struct qlist_head to_free = QLIST_INIT;
276 
277 	on_each_cpu(per_cpu_remove_cache, cache, 1);
278 
279 	spin_lock_irqsave(&quarantine_lock, flags);
280 	qlist_move_cache(&global_quarantine, &to_free, cache);
281 	spin_unlock_irqrestore(&quarantine_lock, flags);
282 
283 	qlist_free_all(&to_free, cache);
284 }
285