393 lines
10 KiB
C
393 lines
10 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* KASAN quarantine.
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*
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* Author: Alexander Potapenko <glider@google.com>
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* Copyright (C) 2016 Google, Inc.
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*
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* Based on code by Dmitry Chernenkov.
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*/
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#include <linux/gfp.h>
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#include <linux/hash.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/percpu.h>
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#include <linux/printk.h>
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#include <linux/shrinker.h>
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#include <linux/slab.h>
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#include <linux/srcu.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/cpuhotplug.h>
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#include "../slab.h"
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#include "kasan.h"
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/* Data structure and operations for quarantine queues. */
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/*
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* Each queue is a single-linked list, which also stores the total size of
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* objects inside of it.
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*/
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struct qlist_head {
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struct qlist_node *head;
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struct qlist_node *tail;
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size_t bytes;
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bool offline;
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};
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#define QLIST_INIT { NULL, NULL, 0 }
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static bool qlist_empty(struct qlist_head *q)
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{
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return !q->head;
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}
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static void qlist_init(struct qlist_head *q)
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{
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q->head = q->tail = NULL;
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q->bytes = 0;
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}
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static void qlist_put(struct qlist_head *q, struct qlist_node *qlink,
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size_t size)
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{
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if (unlikely(qlist_empty(q)))
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q->head = qlink;
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else
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q->tail->next = qlink;
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q->tail = qlink;
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qlink->next = NULL;
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q->bytes += size;
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}
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static void qlist_move_all(struct qlist_head *from, struct qlist_head *to)
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{
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if (unlikely(qlist_empty(from)))
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return;
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if (qlist_empty(to)) {
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*to = *from;
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qlist_init(from);
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return;
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}
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to->tail->next = from->head;
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to->tail = from->tail;
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to->bytes += from->bytes;
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qlist_init(from);
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}
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#define QUARANTINE_PERCPU_SIZE (1 << 20)
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#define QUARANTINE_BATCHES \
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(1024 > 4 * CONFIG_NR_CPUS ? 1024 : 4 * CONFIG_NR_CPUS)
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/*
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* The object quarantine consists of per-cpu queues and a global queue,
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* guarded by quarantine_lock.
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*/
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static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine);
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/* Round-robin FIFO array of batches. */
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static struct qlist_head global_quarantine[QUARANTINE_BATCHES];
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static int quarantine_head;
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static int quarantine_tail;
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/* Total size of all objects in global_quarantine across all batches. */
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static unsigned long quarantine_size;
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static DEFINE_RAW_SPINLOCK(quarantine_lock);
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DEFINE_STATIC_SRCU(remove_cache_srcu);
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/* Maximum size of the global queue. */
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static unsigned long quarantine_max_size;
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/*
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* Target size of a batch in global_quarantine.
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* Usually equal to QUARANTINE_PERCPU_SIZE unless we have too much RAM.
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*/
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static unsigned long quarantine_batch_size;
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/*
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* The fraction of physical memory the quarantine is allowed to occupy.
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* Quarantine doesn't support memory shrinker with SLAB allocator, so we keep
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* the ratio low to avoid OOM.
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*/
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#define QUARANTINE_FRACTION 32
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static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink)
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{
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return virt_to_slab(qlink)->slab_cache;
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}
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static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache)
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{
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struct kasan_free_meta *free_info =
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container_of(qlink, struct kasan_free_meta,
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quarantine_link);
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return ((void *)free_info) - cache->kasan_info.free_meta_offset;
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}
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static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
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{
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void *object = qlink_to_object(qlink, cache);
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struct kasan_free_meta *meta = kasan_get_free_meta(cache, object);
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unsigned long flags;
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if (IS_ENABLED(CONFIG_SLAB))
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local_irq_save(flags);
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/*
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* If init_on_free is enabled and KASAN's free metadata is stored in
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* the object, zero the metadata. Otherwise, the object's memory will
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* not be properly zeroed, as KASAN saves the metadata after the slab
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* allocator zeroes the object.
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*/
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if (slab_want_init_on_free(cache) &&
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cache->kasan_info.free_meta_offset == 0)
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memzero_explicit(meta, sizeof(*meta));
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/*
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* As the object now gets freed from the quarantine, assume that its
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* free track is no longer valid.
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*/
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*(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREE;
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___cache_free(cache, object, _THIS_IP_);
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if (IS_ENABLED(CONFIG_SLAB))
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local_irq_restore(flags);
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}
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static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache)
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{
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struct qlist_node *qlink;
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if (unlikely(qlist_empty(q)))
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return;
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qlink = q->head;
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while (qlink) {
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struct kmem_cache *obj_cache =
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cache ? cache : qlink_to_cache(qlink);
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struct qlist_node *next = qlink->next;
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qlink_free(qlink, obj_cache);
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qlink = next;
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}
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qlist_init(q);
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}
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bool kasan_quarantine_put(struct kmem_cache *cache, void *object)
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{
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unsigned long flags;
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struct qlist_head *q;
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struct qlist_head temp = QLIST_INIT;
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struct kasan_free_meta *meta = kasan_get_free_meta(cache, object);
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/*
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* If there's no metadata for this object, don't put it into
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* quarantine.
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*/
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if (!meta)
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return false;
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/*
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* Note: irq must be disabled until after we move the batch to the
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* global quarantine. Otherwise kasan_quarantine_remove_cache() can
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* miss some objects belonging to the cache if they are in our local
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* temp list. kasan_quarantine_remove_cache() executes on_each_cpu()
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* at the beginning which ensures that it either sees the objects in
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* per-cpu lists or in the global quarantine.
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*/
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local_irq_save(flags);
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q = this_cpu_ptr(&cpu_quarantine);
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if (q->offline) {
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local_irq_restore(flags);
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return false;
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}
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qlist_put(q, &meta->quarantine_link, cache->size);
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if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
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qlist_move_all(q, &temp);
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raw_spin_lock(&quarantine_lock);
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WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes);
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qlist_move_all(&temp, &global_quarantine[quarantine_tail]);
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if (global_quarantine[quarantine_tail].bytes >=
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READ_ONCE(quarantine_batch_size)) {
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int new_tail;
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new_tail = quarantine_tail + 1;
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if (new_tail == QUARANTINE_BATCHES)
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new_tail = 0;
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if (new_tail != quarantine_head)
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quarantine_tail = new_tail;
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}
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raw_spin_unlock(&quarantine_lock);
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}
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local_irq_restore(flags);
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return true;
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}
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void kasan_quarantine_reduce(void)
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{
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size_t total_size, new_quarantine_size, percpu_quarantines;
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unsigned long flags;
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int srcu_idx;
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struct qlist_head to_free = QLIST_INIT;
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if (likely(READ_ONCE(quarantine_size) <=
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READ_ONCE(quarantine_max_size)))
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return;
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/*
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* srcu critical section ensures that kasan_quarantine_remove_cache()
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* will not miss objects belonging to the cache while they are in our
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* local to_free list. srcu is chosen because (1) it gives us private
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* grace period domain that does not interfere with anything else,
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* and (2) it allows synchronize_srcu() to return without waiting
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* if there are no pending read critical sections (which is the
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* expected case).
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*/
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srcu_idx = srcu_read_lock(&remove_cache_srcu);
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raw_spin_lock_irqsave(&quarantine_lock, flags);
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/*
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* Update quarantine size in case of hotplug. Allocate a fraction of
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* the installed memory to quarantine minus per-cpu queue limits.
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*/
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total_size = (totalram_pages() << PAGE_SHIFT) /
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QUARANTINE_FRACTION;
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percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus();
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new_quarantine_size = (total_size < percpu_quarantines) ?
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0 : total_size - percpu_quarantines;
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WRITE_ONCE(quarantine_max_size, new_quarantine_size);
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/* Aim at consuming at most 1/2 of slots in quarantine. */
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WRITE_ONCE(quarantine_batch_size, max((size_t)QUARANTINE_PERCPU_SIZE,
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2 * total_size / QUARANTINE_BATCHES));
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if (likely(quarantine_size > quarantine_max_size)) {
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qlist_move_all(&global_quarantine[quarantine_head], &to_free);
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WRITE_ONCE(quarantine_size, quarantine_size - to_free.bytes);
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quarantine_head++;
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if (quarantine_head == QUARANTINE_BATCHES)
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quarantine_head = 0;
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}
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raw_spin_unlock_irqrestore(&quarantine_lock, flags);
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qlist_free_all(&to_free, NULL);
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srcu_read_unlock(&remove_cache_srcu, srcu_idx);
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}
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static void qlist_move_cache(struct qlist_head *from,
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struct qlist_head *to,
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struct kmem_cache *cache)
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{
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struct qlist_node *curr;
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if (unlikely(qlist_empty(from)))
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return;
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curr = from->head;
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qlist_init(from);
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while (curr) {
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struct qlist_node *next = curr->next;
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struct kmem_cache *obj_cache = qlink_to_cache(curr);
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if (obj_cache == cache)
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qlist_put(to, curr, obj_cache->size);
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else
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qlist_put(from, curr, obj_cache->size);
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curr = next;
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}
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}
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static void per_cpu_remove_cache(void *arg)
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{
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struct kmem_cache *cache = arg;
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struct qlist_head to_free = QLIST_INIT;
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struct qlist_head *q;
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q = this_cpu_ptr(&cpu_quarantine);
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/*
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* Ensure the ordering between the writing to q->offline and
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* per_cpu_remove_cache. Prevent cpu_quarantine from being corrupted
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* by interrupt.
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*/
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if (READ_ONCE(q->offline))
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return;
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qlist_move_cache(q, &to_free, cache);
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qlist_free_all(&to_free, cache);
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}
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/* Free all quarantined objects belonging to cache. */
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void kasan_quarantine_remove_cache(struct kmem_cache *cache)
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{
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unsigned long flags, i;
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struct qlist_head to_free = QLIST_INIT;
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/*
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* Must be careful to not miss any objects that are being moved from
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* per-cpu list to the global quarantine in kasan_quarantine_put(),
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* nor objects being freed in kasan_quarantine_reduce(). on_each_cpu()
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* achieves the first goal, while synchronize_srcu() achieves the
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* second.
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*/
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on_each_cpu(per_cpu_remove_cache, cache, 1);
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raw_spin_lock_irqsave(&quarantine_lock, flags);
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for (i = 0; i < QUARANTINE_BATCHES; i++) {
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if (qlist_empty(&global_quarantine[i]))
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continue;
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qlist_move_cache(&global_quarantine[i], &to_free, cache);
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/* Scanning whole quarantine can take a while. */
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raw_spin_unlock_irqrestore(&quarantine_lock, flags);
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cond_resched();
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raw_spin_lock_irqsave(&quarantine_lock, flags);
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}
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raw_spin_unlock_irqrestore(&quarantine_lock, flags);
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qlist_free_all(&to_free, cache);
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synchronize_srcu(&remove_cache_srcu);
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}
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static int kasan_cpu_online(unsigned int cpu)
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{
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this_cpu_ptr(&cpu_quarantine)->offline = false;
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return 0;
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}
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static int kasan_cpu_offline(unsigned int cpu)
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{
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struct qlist_head *q;
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q = this_cpu_ptr(&cpu_quarantine);
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/* Ensure the ordering between the writing to q->offline and
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|
|
* qlist_free_all. Otherwise, cpu_quarantine may be corrupted
|
||
|
|
* by interrupt.
|
||
|
|
*/
|
||
|
|
WRITE_ONCE(q->offline, true);
|
||
|
|
barrier();
|
||
|
|
qlist_free_all(q, NULL);
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
static int __init kasan_cpu_quarantine_init(void)
|
||
|
|
{
|
||
|
|
int ret = 0;
|
||
|
|
|
||
|
|
ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/kasan:online",
|
||
|
|
kasan_cpu_online, kasan_cpu_offline);
|
||
|
|
if (ret < 0)
|
||
|
|
pr_err("kasan cpu quarantine register failed [%d]\n", ret);
|
||
|
|
return ret;
|
||
|
|
}
|
||
|
|
late_initcall(kasan_cpu_quarantine_init);
|