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 unsigned long flags; 148 149 if (IS_ENABLED(CONFIG_SLAB)) 150 local_irq_save(flags); 151 152 ___cache_free(cache, object, _THIS_IP_); 153 154 if (IS_ENABLED(CONFIG_SLAB)) 155 local_irq_restore(flags); 156 } 157 158 static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache) 159 { 160 struct qlist_node *qlink; 161 162 if (unlikely(qlist_empty(q))) 163 return; 164 165 qlink = q->head; 166 while (qlink) { 167 struct kmem_cache *obj_cache = 168 cache ? cache : qlink_to_cache(qlink); 169 struct qlist_node *next = qlink->next; 170 171 qlink_free(qlink, obj_cache); 172 qlink = next; 173 } 174 qlist_init(q); 175 } 176 177 void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache) 178 { 179 unsigned long flags; 180 struct qlist_head *q; 181 struct qlist_head temp = QLIST_INIT; 182 183 local_irq_save(flags); 184 185 q = this_cpu_ptr(&cpu_quarantine); 186 qlist_put(q, &info->quarantine_link, cache->size); 187 if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) 188 qlist_move_all(q, &temp); 189 190 local_irq_restore(flags); 191 192 if (unlikely(!qlist_empty(&temp))) { 193 spin_lock_irqsave(&quarantine_lock, flags); 194 qlist_move_all(&temp, &global_quarantine); 195 spin_unlock_irqrestore(&quarantine_lock, flags); 196 } 197 } 198 199 void quarantine_reduce(void) 200 { 201 size_t new_quarantine_size, percpu_quarantines; 202 unsigned long flags; 203 struct qlist_head to_free = QLIST_INIT; 204 size_t size_to_free = 0; 205 struct qlist_node *last; 206 207 if (likely(READ_ONCE(global_quarantine.bytes) <= 208 READ_ONCE(quarantine_size))) 209 return; 210 211 spin_lock_irqsave(&quarantine_lock, flags); 212 213 /* 214 * Update quarantine size in case of hotplug. Allocate a fraction of 215 * the installed memory to quarantine minus per-cpu queue limits. 216 */ 217 new_quarantine_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) / 218 QUARANTINE_FRACTION; 219 percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus(); 220 if (WARN_ONCE(new_quarantine_size < percpu_quarantines, 221 "Too little memory, disabling global KASAN quarantine.\n")) 222 new_quarantine_size = 0; 223 else 224 new_quarantine_size -= percpu_quarantines; 225 WRITE_ONCE(quarantine_size, new_quarantine_size); 226 227 last = global_quarantine.head; 228 while (last) { 229 struct kmem_cache *cache = qlink_to_cache(last); 230 231 size_to_free += cache->size; 232 if (!last->next || size_to_free > 233 global_quarantine.bytes - QUARANTINE_LOW_SIZE) 234 break; 235 last = last->next; 236 } 237 qlist_move(&global_quarantine, last, &to_free, size_to_free); 238 239 spin_unlock_irqrestore(&quarantine_lock, flags); 240 241 qlist_free_all(&to_free, NULL); 242 } 243 244 static void qlist_move_cache(struct qlist_head *from, 245 struct qlist_head *to, 246 struct kmem_cache *cache) 247 { 248 struct qlist_node *curr; 249 250 if (unlikely(qlist_empty(from))) 251 return; 252 253 curr = from->head; 254 qlist_init(from); 255 while (curr) { 256 struct qlist_node *next = curr->next; 257 struct kmem_cache *obj_cache = qlink_to_cache(curr); 258 259 if (obj_cache == cache) 260 qlist_put(to, curr, obj_cache->size); 261 else 262 qlist_put(from, curr, obj_cache->size); 263 264 curr = next; 265 } 266 } 267 268 static void per_cpu_remove_cache(void *arg) 269 { 270 struct kmem_cache *cache = arg; 271 struct qlist_head to_free = QLIST_INIT; 272 struct qlist_head *q; 273 274 q = this_cpu_ptr(&cpu_quarantine); 275 qlist_move_cache(q, &to_free, cache); 276 qlist_free_all(&to_free, cache); 277 } 278 279 void quarantine_remove_cache(struct kmem_cache *cache) 280 { 281 unsigned long flags; 282 struct qlist_head to_free = QLIST_INIT; 283 284 on_each_cpu(per_cpu_remove_cache, cache, 1); 285 286 spin_lock_irqsave(&quarantine_lock, flags); 287 qlist_move_cache(&global_quarantine, &to_free, cache); 288 spin_unlock_irqrestore(&quarantine_lock, flags); 289 290 qlist_free_all(&to_free, cache); 291 } 292