mm/kasan/quarantine.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * KASAN quarantine.
  *
  * Author: Alexander Potapenko <glider@google.com>
  * Copyright (C) 2016 Google, Inc.
  *
  * Based on code by Dmitry Chernenkov.
  */

 #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/srcu.h>
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/cpuhotplug.h>

 #include "../slab.h"
 #include "kasan.h"

 /* Data structure and operations for quarantine queues. */

 /*
  * Each queue is a single-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;
 	bool offline;
 };

 #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);
 }

 #define QUARANTINE_PERCPU_SIZE (1 << 20)
 #define QUARANTINE_BATCHES \
 	(1024 > 4 * CONFIG_NR_CPUS ? 1024 : 4 * CONFIG_NR_CPUS)

 /*
  * 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);

 /* Round-robin FIFO array of batches. */
 static struct qlist_head global_quarantine[QUARANTINE_BATCHES];
 static int quarantine_head;
 static int quarantine_tail;
 /* Total size of all objects in global_quarantine across all batches. */
 static unsigned long quarantine_size;
 static DEFINE_RAW_SPINLOCK(quarantine_lock);
 DEFINE_STATIC_SRCU(remove_cache_srcu);

 /* Maximum size of the global queue. */
 static unsigned long quarantine_max_size;

 /*
  * Target size of a batch in global_quarantine.
  * Usually equal to QUARANTINE_PERCPU_SIZE unless we have too much RAM.
  */
 static unsigned long quarantine_batch_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

 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);

 	/*
 	 * As the object now gets freed from the quarantine, assume that its
 	 * free track is no longer valid.
 	 */
 	*(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREE;

 	___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);
 }

 bool kasan_quarantine_put(struct kmem_cache *cache, void *object)
 {
 	unsigned long flags;
 	struct qlist_head *q;
 	struct qlist_head temp = QLIST_INIT;
 	struct kasan_free_meta *meta = kasan_get_free_meta(cache, object);

 	/*
 	 * If there's no metadata for this object, don't put it into
 	 * quarantine.
 	 */
 	if (!meta)
 		return false;

 	/*
 	 * Note: irq must be disabled until after we move the batch to the
 	 * global quarantine. Otherwise kasan_quarantine_remove_cache() can
 	 * miss some objects belonging to the cache if they are in our local
 	 * temp list. kasan_quarantine_remove_cache() executes on_each_cpu()
 	 * at the beginning which ensures that it either sees the objects in
 	 * per-cpu lists or in the global quarantine.
 	 */
 	local_irq_save(flags);

 	q = this_cpu_ptr(&cpu_quarantine);
 	if (q->offline) {
 		local_irq_restore(flags);
 		return false;
 	}
 	qlist_put(q, &meta->quarantine_link, cache->size);
 	if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
 		qlist_move_all(q, &temp);

 		raw_spin_lock(&quarantine_lock);
 		WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes);
 		qlist_move_all(&temp, &global_quarantine[quarantine_tail]);
 		if (global_quarantine[quarantine_tail].bytes >=
 				READ_ONCE(quarantine_batch_size)) {
 			int new_tail;

 			new_tail = quarantine_tail + 1;
 			if (new_tail == QUARANTINE_BATCHES)
 				new_tail = 0;
 			if (new_tail != quarantine_head)
 				quarantine_tail = new_tail;
 		}
 		raw_spin_unlock(&quarantine_lock);
 	}

 	local_irq_restore(flags);

 	return true;
 }

 void kasan_quarantine_reduce(void)
 {
 	size_t total_size, new_quarantine_size, percpu_quarantines;
 	unsigned long flags;
 	int srcu_idx;
 	struct qlist_head to_free = QLIST_INIT;

 	if (likely(READ_ONCE(quarantine_size) <=
 		   READ_ONCE(quarantine_max_size)))
 		return;

 	/*
 	 * srcu critical section ensures that kasan_quarantine_remove_cache()
 	 * will not miss objects belonging to the cache while they are in our
 	 * local to_free list. srcu is chosen because (1) it gives us private
 	 * grace period domain that does not interfere with anything else,
 	 * and (2) it allows synchronize_srcu() to return without waiting
 	 * if there are no pending read critical sections (which is the
 	 * expected case).
 	 */
 	srcu_idx = srcu_read_lock(&remove_cache_srcu);
 	raw_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.
 	 */
 	total_size = (totalram_pages() << PAGE_SHIFT) /
 		QUARANTINE_FRACTION;
 	percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus();
 	new_quarantine_size = (total_size < percpu_quarantines) ?
 		0 : total_size - percpu_quarantines;
 	WRITE_ONCE(quarantine_max_size, new_quarantine_size);
 	/* Aim at consuming at most 1/2 of slots in quarantine. */
 	WRITE_ONCE(quarantine_batch_size, max((size_t)QUARANTINE_PERCPU_SIZE,
 		2 * total_size / QUARANTINE_BATCHES));

 	if (likely(quarantine_size > quarantine_max_size)) {
 		qlist_move_all(&global_quarantine[quarantine_head], &to_free);
 		WRITE_ONCE(quarantine_size, quarantine_size - to_free.bytes);
 		quarantine_head++;
 		if (quarantine_head == QUARANTINE_BATCHES)
 			quarantine_head = 0;
 	}

 	raw_spin_unlock_irqrestore(&quarantine_lock, flags);

 	qlist_free_all(&to_free, NULL);
 	srcu_read_unlock(&remove_cache_srcu, srcu_idx);
 }

 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);
 }

 /* Free all quarantined objects belonging to cache. */
 void kasan_quarantine_remove_cache(struct kmem_cache *cache)
 {
 	unsigned long flags, i;
 	struct qlist_head to_free = QLIST_INIT;

 	/*
 	 * Must be careful to not miss any objects that are being moved from
 	 * per-cpu list to the global quarantine in kasan_quarantine_put(),
 	 * nor objects being freed in kasan_quarantine_reduce(). on_each_cpu()
 	 * achieves the first goal, while synchronize_srcu() achieves the
 	 * second.
 	 */
 	on_each_cpu(per_cpu_remove_cache, cache, 1);

 	raw_spin_lock_irqsave(&quarantine_lock, flags);
 	for (i = 0; i < QUARANTINE_BATCHES; i++) {
 		if (qlist_empty(&global_quarantine[i]))
 			continue;
 		qlist_move_cache(&global_quarantine[i], &to_free, cache);
 		/* Scanning whole quarantine can take a while. */
 		raw_spin_unlock_irqrestore(&quarantine_lock, flags);
 		cond_resched();
 		raw_spin_lock_irqsave(&quarantine_lock, flags);
 	}
 	raw_spin_unlock_irqrestore(&quarantine_lock, flags);

 	qlist_free_all(&to_free, cache);

 	synchronize_srcu(&remove_cache_srcu);
 }

 static int kasan_cpu_online(unsigned int cpu)
 {
 	this_cpu_ptr(&cpu_quarantine)->offline = false;
 	return 0;
 }

 static int kasan_cpu_offline(unsigned int cpu)
 {
 	struct qlist_head *q;

 	q = this_cpu_ptr(&cpu_quarantine);
 	/* Ensure the ordering between the writing to q->offline and
 	 * 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);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* KASAN quarantine.
	*
	* Author: Alexander Potapenko <glider@google.com>
	* Copyright (C) 2016 Google, Inc.
	*
	* Based on code by Dmitry Chernenkov.
	*/

	#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/srcu.h>
	#include <linux/string.h>
	#include <linux/types.h>
	#include <linux/cpuhotplug.h>

	#include "../slab.h"
	#include "kasan.h"

	/* Data structure and operations for quarantine queues. */

	/*
	* Each queue is a single-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;
	bool offline;
	};

	#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);
	}

	#define QUARANTINE_PERCPU_SIZE (1 << 20)
	#define QUARANTINE_BATCHES \
	(1024 > 4 * CONFIG_NR_CPUS ? 1024 : 4 * CONFIG_NR_CPUS)

	/*
	* 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);

	/* Round-robin FIFO array of batches. */
	static struct qlist_head global_quarantine[QUARANTINE_BATCHES];
	static int quarantine_head;
	static int quarantine_tail;
	/* Total size of all objects in global_quarantine across all batches. */
	static unsigned long quarantine_size;
	static DEFINE_RAW_SPINLOCK(quarantine_lock);
	DEFINE_STATIC_SRCU(remove_cache_srcu);

	/* Maximum size of the global queue. */
	static unsigned long quarantine_max_size;

	/*
	* Target size of a batch in global_quarantine.
	* Usually equal to QUARANTINE_PERCPU_SIZE unless we have too much RAM.
	*/
	static unsigned long quarantine_batch_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

	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);

	/*
	* As the object now gets freed from the quarantine, assume that its
	* free track is no longer valid.
	*/
	(u8 )kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREE;

	___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);
	}

	bool kasan_quarantine_put(struct kmem_cache cache, void object)
	{
	unsigned long flags;
	struct qlist_head *q;
	struct qlist_head temp = QLIST_INIT;
	struct kasan_free_meta *meta = kasan_get_free_meta(cache, object);

	/*
	* If there's no metadata for this object, don't put it into
	* quarantine.
	*/
	if (!meta)
	return false;

	/*
	* Note: irq must be disabled until after we move the batch to the
	* global quarantine. Otherwise kasan_quarantine_remove_cache() can
	* miss some objects belonging to the cache if they are in our local
	* temp list. kasan_quarantine_remove_cache() executes on_each_cpu()
	* at the beginning which ensures that it either sees the objects in
	* per-cpu lists or in the global quarantine.
	*/
	local_irq_save(flags);

	q = this_cpu_ptr(&cpu_quarantine);
	if (q->offline) {
	local_irq_restore(flags);
	return false;
	}
	qlist_put(q, &meta->quarantine_link, cache->size);
	if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
	qlist_move_all(q, &temp);

	raw_spin_lock(&quarantine_lock);
	WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes);
	qlist_move_all(&temp, &global_quarantine[quarantine_tail]);
	if (global_quarantine[quarantine_tail].bytes >=
	READ_ONCE(quarantine_batch_size)) {
	int new_tail;

	new_tail = quarantine_tail + 1;
	if (new_tail == QUARANTINE_BATCHES)
	new_tail = 0;
	if (new_tail != quarantine_head)
	quarantine_tail = new_tail;
	}
	raw_spin_unlock(&quarantine_lock);
	}

	local_irq_restore(flags);

	return true;
	}

	void kasan_quarantine_reduce(void)
	{
	size_t total_size, new_quarantine_size, percpu_quarantines;
	unsigned long flags;
	int srcu_idx;
	struct qlist_head to_free = QLIST_INIT;

	if (likely(READ_ONCE(quarantine_size) <=
	READ_ONCE(quarantine_max_size)))
	return;

	/*
	* srcu critical section ensures that kasan_quarantine_remove_cache()
	* will not miss objects belonging to the cache while they are in our
	* local to_free list. srcu is chosen because (1) it gives us private
	* grace period domain that does not interfere with anything else,
	* and (2) it allows synchronize_srcu() to return without waiting
	* if there are no pending read critical sections (which is the
	* expected case).
	*/
	srcu_idx = srcu_read_lock(&remove_cache_srcu);
	raw_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.
	*/
	total_size = (totalram_pages() << PAGE_SHIFT) /
	QUARANTINE_FRACTION;
	percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus();
	new_quarantine_size = (total_size < percpu_quarantines) ?
	0 : total_size - percpu_quarantines;
	WRITE_ONCE(quarantine_max_size, new_quarantine_size);
	/* Aim at consuming at most 1/2 of slots in quarantine. */
	WRITE_ONCE(quarantine_batch_size, max((size_t)QUARANTINE_PERCPU_SIZE,
	2 * total_size / QUARANTINE_BATCHES));

	if (likely(quarantine_size > quarantine_max_size)) {
	qlist_move_all(&global_quarantine[quarantine_head], &to_free);
	WRITE_ONCE(quarantine_size, quarantine_size - to_free.bytes);
	quarantine_head++;
	if (quarantine_head == QUARANTINE_BATCHES)
	quarantine_head = 0;
	}

	raw_spin_unlock_irqrestore(&quarantine_lock, flags);

	qlist_free_all(&to_free, NULL);
	srcu_read_unlock(&remove_cache_srcu, srcu_idx);
	}

	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);
	}

	/* Free all quarantined objects belonging to cache. */
	void kasan_quarantine_remove_cache(struct kmem_cache *cache)
	{
	unsigned long flags, i;
	struct qlist_head to_free = QLIST_INIT;

	/*
	* Must be careful to not miss any objects that are being moved from
	* per-cpu list to the global quarantine in kasan_quarantine_put(),
	* nor objects being freed in kasan_quarantine_reduce(). on_each_cpu()
	* achieves the first goal, while synchronize_srcu() achieves the
	* second.
	*/
	on_each_cpu(per_cpu_remove_cache, cache, 1);

	raw_spin_lock_irqsave(&quarantine_lock, flags);
	for (i = 0; i < QUARANTINE_BATCHES; i++) {
	if (qlist_empty(&global_quarantine[i]))
	continue;
	qlist_move_cache(&global_quarantine[i], &to_free, cache);
	/* Scanning whole quarantine can take a while. */
	raw_spin_unlock_irqrestore(&quarantine_lock, flags);
	cond_resched();
	raw_spin_lock_irqsave(&quarantine_lock, flags);
	}
	raw_spin_unlock_irqrestore(&quarantine_lock, flags);

	qlist_free_all(&to_free, cache);

	synchronize_srcu(&remove_cache_srcu);
	}

	static int kasan_cpu_online(unsigned int cpu)
	{
	this_cpu_ptr(&cpu_quarantine)->offline = false;
	return 0;
	}

	static int kasan_cpu_offline(unsigned int cpu)
	{
	struct qlist_head *q;

	q = this_cpu_ptr(&cpu_quarantine);
	/* Ensure the ordering between the writing to q->offline and
	* 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);