blob: b6728a33a4aca104fde8022b90fdf2df5630af31 [file] [log] [blame]
/*
* KASAN quarantine.
*
* Author: Alexander Potapenko <glider@google.com>
* Copyright (C) 2016 Google, Inc.
*
* Based on code by Dmitry Chernenkov.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* version 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
*/
#include <linux/gfp.h>
#include <linux/hash.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/percpu.h>
#include <linux/printk.h>
#include <linux/shrinker.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/types.h>
#include "../slab.h"
#include "kasan.h"
/* Data structure and operations for quarantine queues. */
/*
* Each queue is a signle-linked list, which also stores the total size of
* objects inside of it.
*/
struct qlist_head {
struct qlist_node *head;
struct qlist_node *tail;
size_t bytes;
};
#define QLIST_INIT { NULL, NULL, 0 }
static bool qlist_empty(struct qlist_head *q)
{
return !q->head;
}
static void qlist_init(struct qlist_head *q)
{
q->head = q->tail = NULL;
q->bytes = 0;
}
static void qlist_put(struct qlist_head *q, struct qlist_node *qlink,
size_t size)
{
if (unlikely(qlist_empty(q)))
q->head = qlink;
else
q->tail->next = qlink;
q->tail = qlink;
qlink->next = NULL;
q->bytes += size;
}
static void qlist_move_all(struct qlist_head *from, struct qlist_head *to)
{
if (unlikely(qlist_empty(from)))
return;
if (qlist_empty(to)) {
*to = *from;
qlist_init(from);
return;
}
to->tail->next = from->head;
to->tail = from->tail;
to->bytes += from->bytes;
qlist_init(from);
}
static void qlist_move(struct qlist_head *from, struct qlist_node *last,
struct qlist_head *to, size_t size)
{
if (unlikely(last == from->tail)) {
qlist_move_all(from, to);
return;
}
if (qlist_empty(to))
to->head = from->head;
else
to->tail->next = from->head;
to->tail = last;
from->head = last->next;
last->next = NULL;
from->bytes -= size;
to->bytes += size;
}
/*
* The object quarantine consists of per-cpu queues and a global queue,
* guarded by quarantine_lock.
*/
static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine);
static struct qlist_head global_quarantine;
static DEFINE_SPINLOCK(quarantine_lock);
/* Maximum size of the global queue. */
static unsigned long quarantine_size;
/*
* The fraction of physical memory the quarantine is allowed to occupy.
* Quarantine doesn't support memory shrinker with SLAB allocator, so we keep
* the ratio low to avoid OOM.
*/
#define QUARANTINE_FRACTION 32
#define QUARANTINE_LOW_SIZE (READ_ONCE(quarantine_size) * 3 / 4)
#define QUARANTINE_PERCPU_SIZE (1 << 20)
static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink)
{
return virt_to_head_page(qlink)->slab_cache;
}
static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache)
{
struct kasan_free_meta *free_info =
container_of(qlink, struct kasan_free_meta,
quarantine_link);
return ((void *)free_info) - cache->kasan_info.free_meta_offset;
}
static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
{
void *object = qlink_to_object(qlink, cache);
unsigned long flags;
if (IS_ENABLED(CONFIG_SLAB))
local_irq_save(flags);
___cache_free(cache, object, _THIS_IP_);
if (IS_ENABLED(CONFIG_SLAB))
local_irq_restore(flags);
}
static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache)
{
struct qlist_node *qlink;
if (unlikely(qlist_empty(q)))
return;
qlink = q->head;
while (qlink) {
struct kmem_cache *obj_cache =
cache ? cache : qlink_to_cache(qlink);
struct qlist_node *next = qlink->next;
qlink_free(qlink, obj_cache);
qlink = next;
}
qlist_init(q);
}
void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
{
unsigned long flags;
struct qlist_head *q;
struct qlist_head temp = QLIST_INIT;
local_irq_save(flags);
q = this_cpu_ptr(&cpu_quarantine);
qlist_put(q, &info->quarantine_link, cache->size);
if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE))
qlist_move_all(q, &temp);
local_irq_restore(flags);
if (unlikely(!qlist_empty(&temp))) {
spin_lock_irqsave(&quarantine_lock, flags);
qlist_move_all(&temp, &global_quarantine);
spin_unlock_irqrestore(&quarantine_lock, flags);
}
}
void quarantine_reduce(void)
{
size_t new_quarantine_size, percpu_quarantines;
unsigned long flags;
struct qlist_head to_free = QLIST_INIT;
size_t size_to_free = 0;
struct qlist_node *last;
if (likely(READ_ONCE(global_quarantine.bytes) <=
READ_ONCE(quarantine_size)))
return;
spin_lock_irqsave(&quarantine_lock, flags);
/*
* Update quarantine size in case of hotplug. Allocate a fraction of
* the installed memory to quarantine minus per-cpu queue limits.
*/
new_quarantine_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) /
QUARANTINE_FRACTION;
percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus();
if (WARN_ONCE(new_quarantine_size < percpu_quarantines,
"Too little memory, disabling global KASAN quarantine.\n"))
new_quarantine_size = 0;
else
new_quarantine_size -= percpu_quarantines;
WRITE_ONCE(quarantine_size, new_quarantine_size);
last = global_quarantine.head;
while (last) {
struct kmem_cache *cache = qlink_to_cache(last);
size_to_free += cache->size;
if (!last->next || size_to_free >
global_quarantine.bytes - QUARANTINE_LOW_SIZE)
break;
last = last->next;
}
qlist_move(&global_quarantine, last, &to_free, size_to_free);
spin_unlock_irqrestore(&quarantine_lock, flags);
qlist_free_all(&to_free, NULL);
}
static void qlist_move_cache(struct qlist_head *from,
struct qlist_head *to,
struct kmem_cache *cache)
{
struct qlist_node *curr;
if (unlikely(qlist_empty(from)))
return;
curr = from->head;
qlist_init(from);
while (curr) {
struct qlist_node *next = curr->next;
struct kmem_cache *obj_cache = qlink_to_cache(curr);
if (obj_cache == cache)
qlist_put(to, curr, obj_cache->size);
else
qlist_put(from, curr, obj_cache->size);
curr = next;
}
}
static void per_cpu_remove_cache(void *arg)
{
struct kmem_cache *cache = arg;
struct qlist_head to_free = QLIST_INIT;
struct qlist_head *q;
q = this_cpu_ptr(&cpu_quarantine);
qlist_move_cache(q, &to_free, cache);
qlist_free_all(&to_free, cache);
}
void quarantine_remove_cache(struct kmem_cache *cache)
{
unsigned long flags;
struct qlist_head to_free = QLIST_INIT;
on_each_cpu(per_cpu_remove_cache, cache, 1);
spin_lock_irqsave(&quarantine_lock, flags);
qlist_move_cache(&global_quarantine, &to_free, cache);
spin_unlock_irqrestore(&quarantine_lock, flags);
qlist_free_all(&to_free, cache);
}