mm/kasan/quarantine.c

   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         new_quarantine_size = (new_quarantine_size < percpu_quarantines) ?
 221                 0 : new_quarantine_size - percpu_quarantines;
 222         WRITE_ONCE(quarantine_size, new_quarantine_size);
 223
 224         last = global_quarantine.head;
 225         while (last) {
 226                 struct kmem_cache *cache = qlink_to_cache(last);
 227
 228                 size_to_free += cache->size;
 229                 if (!last->next || size_to_free >
 230                     global_quarantine.bytes - QUARANTINE_LOW_SIZE)
 231                         break;
 232                 last = last->next;
 233         }
 234         qlist_move(&global_quarantine, last, &to_free, size_to_free);
 235
 236         spin_unlock_irqrestore(&quarantine_lock, flags);
 237
 238         qlist_free_all(&to_free, NULL);
 239 }
 240
 241 static void qlist_move_cache(struct qlist_head *from,
 242                                    struct qlist_head *to,
 243                                    struct kmem_cache *cache)
 244 {
 245         struct qlist_node *curr;
 246
 247         if (unlikely(qlist_empty(from)))
 248                 return;
 249
 250         curr = from->head;
 251         qlist_init(from);
 252         while (curr) {
 253                 struct qlist_node *next = curr->next;
 254                 struct kmem_cache *obj_cache = qlink_to_cache(curr);
 255
 256                 if (obj_cache == cache)
 257                         qlist_put(to, curr, obj_cache->size);
 258                 else
 259                         qlist_put(from, curr, obj_cache->size);
 260
 261                 curr = next;
 262         }
 263 }
 264
 265 static void per_cpu_remove_cache(void *arg)
 266 {
 267         struct kmem_cache *cache = arg;
 268         struct qlist_head to_free = QLIST_INIT;
 269         struct qlist_head *q;
 270
 271         q = this_cpu_ptr(&cpu_quarantine);
 272         qlist_move_cache(q, &to_free, cache);
 273         qlist_free_all(&to_free, cache);
 274 }
 275
 276 void quarantine_remove_cache(struct kmem_cache *cache)
 277 {
 278         unsigned long flags;
 279         struct qlist_head to_free = QLIST_INIT;
 280
 281         on_each_cpu(per_cpu_remove_cache, cache, 1);
 282
 283         spin_lock_irqsave(&quarantine_lock, flags);
 284         qlist_move_cache(&global_quarantine, &to_free, cache);
 285         spin_unlock_irqrestore(&quarantine_lock, flags);
 286
 287         qlist_free_all(&to_free, cache);
 288 }