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 #define QUARANTINE_PERCPU_SIZE (1 << 20) 90 #define QUARANTINE_BATCHES \ 91 (1024 > 4 * CONFIG_NR_CPUS ? 1024 : 4 * CONFIG_NR_CPUS) 92 93 /* 94 * The object quarantine consists of per-cpu queues and a global queue, 95 * guarded by quarantine_lock. 96 */ 97 static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine); 98 99 /* Round-robin FIFO array of batches. */ 100 static struct qlist_head global_quarantine[QUARANTINE_BATCHES]; 101 static int quarantine_head; 102 static int quarantine_tail; 103 /* Total size of all objects in global_quarantine across all batches. */ 104 static unsigned long quarantine_size; 105 static DEFINE_SPINLOCK(quarantine_lock); 106 107 /* Maximum size of the global queue. */ 108 static unsigned long quarantine_max_size; 109 110 /* 111 * Target size of a batch in global_quarantine. 112 * Usually equal to QUARANTINE_PERCPU_SIZE unless we have too much RAM. 113 */ 114 static unsigned long quarantine_batch_size; 115 116 /* 117 * The fraction of physical memory the quarantine is allowed to occupy. 118 * Quarantine doesn't support memory shrinker with SLAB allocator, so we keep 119 * the ratio low to avoid OOM. 120 */ 121 #define QUARANTINE_FRACTION 32 122 123 static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink) 124 { 125 return virt_to_head_page(qlink)->slab_cache; 126 } 127 128 static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache) 129 { 130 struct kasan_free_meta *free_info = 131 container_of(qlink, struct kasan_free_meta, 132 quarantine_link); 133 134 return ((void *)free_info) - cache->kasan_info.free_meta_offset; 135 } 136 137 static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache) 138 { 139 void *object = qlink_to_object(qlink, cache); 140 unsigned long flags; 141 142 if (IS_ENABLED(CONFIG_SLAB)) 143 local_irq_save(flags); 144 145 ___cache_free(cache, object, _THIS_IP_); 146 147 if (IS_ENABLED(CONFIG_SLAB)) 148 local_irq_restore(flags); 149 } 150 151 static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache) 152 { 153 struct qlist_node *qlink; 154 155 if (unlikely(qlist_empty(q))) 156 return; 157 158 qlink = q->head; 159 while (qlink) { 160 struct kmem_cache *obj_cache = 161 cache ? cache : qlink_to_cache(qlink); 162 struct qlist_node *next = qlink->next; 163 164 qlink_free(qlink, obj_cache); 165 qlink = next; 166 } 167 qlist_init(q); 168 } 169 170 void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache) 171 { 172 unsigned long flags; 173 struct qlist_head *q; 174 struct qlist_head temp = QLIST_INIT; 175 176 local_irq_save(flags); 177 178 q = this_cpu_ptr(&cpu_quarantine); 179 qlist_put(q, &info->quarantine_link, cache->size); 180 if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) 181 qlist_move_all(q, &temp); 182 183 local_irq_restore(flags); 184 185 if (unlikely(!qlist_empty(&temp))) { 186 spin_lock_irqsave(&quarantine_lock, flags); 187 WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes); 188 qlist_move_all(&temp, &global_quarantine[quarantine_tail]); 189 if (global_quarantine[quarantine_tail].bytes >= 190 READ_ONCE(quarantine_batch_size)) { 191 int new_tail; 192 193 new_tail = quarantine_tail + 1; 194 if (new_tail == QUARANTINE_BATCHES) 195 new_tail = 0; 196 if (new_tail != quarantine_head) 197 quarantine_tail = new_tail; 198 } 199 spin_unlock_irqrestore(&quarantine_lock, flags); 200 } 201 } 202 203 void quarantine_reduce(void) 204 { 205 size_t total_size, new_quarantine_size, percpu_quarantines; 206 unsigned long flags; 207 struct qlist_head to_free = QLIST_INIT; 208 209 if (likely(READ_ONCE(quarantine_size) <= 210 READ_ONCE(quarantine_max_size))) 211 return; 212 213 spin_lock_irqsave(&quarantine_lock, flags); 214 215 /* 216 * Update quarantine size in case of hotplug. Allocate a fraction of 217 * the installed memory to quarantine minus per-cpu queue limits. 218 */ 219 total_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) / 220 QUARANTINE_FRACTION; 221 percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus(); 222 new_quarantine_size = (total_size < percpu_quarantines) ? 223 0 : total_size - percpu_quarantines; 224 WRITE_ONCE(quarantine_max_size, new_quarantine_size); 225 /* Aim at consuming at most 1/2 of slots in quarantine. */ 226 WRITE_ONCE(quarantine_batch_size, max((size_t)QUARANTINE_PERCPU_SIZE, 227 2 * total_size / QUARANTINE_BATCHES)); 228 229 if (likely(quarantine_size > quarantine_max_size)) { 230 qlist_move_all(&global_quarantine[quarantine_head], &to_free); 231 WRITE_ONCE(quarantine_size, quarantine_size - to_free.bytes); 232 quarantine_head++; 233 if (quarantine_head == QUARANTINE_BATCHES) 234 quarantine_head = 0; 235 } 236 237 spin_unlock_irqrestore(&quarantine_lock, flags); 238 239 qlist_free_all(&to_free, NULL); 240 } 241 242 static void qlist_move_cache(struct qlist_head *from, 243 struct qlist_head *to, 244 struct kmem_cache *cache) 245 { 246 struct qlist_node *curr; 247 248 if (unlikely(qlist_empty(from))) 249 return; 250 251 curr = from->head; 252 qlist_init(from); 253 while (curr) { 254 struct qlist_node *next = curr->next; 255 struct kmem_cache *obj_cache = qlink_to_cache(curr); 256 257 if (obj_cache == cache) 258 qlist_put(to, curr, obj_cache->size); 259 else 260 qlist_put(from, curr, obj_cache->size); 261 262 curr = next; 263 } 264 } 265 266 static void per_cpu_remove_cache(void *arg) 267 { 268 struct kmem_cache *cache = arg; 269 struct qlist_head to_free = QLIST_INIT; 270 struct qlist_head *q; 271 272 q = this_cpu_ptr(&cpu_quarantine); 273 qlist_move_cache(q, &to_free, cache); 274 qlist_free_all(&to_free, cache); 275 } 276 277 void quarantine_remove_cache(struct kmem_cache *cache) 278 { 279 unsigned long flags, i; 280 struct qlist_head to_free = QLIST_INIT; 281 282 on_each_cpu(per_cpu_remove_cache, cache, 1); 283 284 spin_lock_irqsave(&quarantine_lock, flags); 285 for (i = 0; i < QUARANTINE_BATCHES; i++) 286 qlist_move_cache(&global_quarantine[i], &to_free, cache); 287 spin_unlock_irqrestore(&quarantine_lock, flags); 288 289 qlist_free_all(&to_free, cache); 290 } 291