1 files changed, 328 insertions, 0 deletions
diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
new file mode 100644
index 000000000..3a8ddf8ba
--- /dev/null
+++ b/mm/kasan/quarantine.c
@@ -0,0 +1,328 @@
+/*
+ * 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/srcu.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);
+}
+
+#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_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);
+
+	___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;
+
+	/*
+	 * Note: irq must be disabled until after we move the batch to the
+	 * global quarantine. Otherwise quarantine_remove_cache() can miss
+	 * some objects belonging to the cache if they are in our local temp
+	 * list. 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);
+	qlist_put(q, &info->quarantine_link, cache->size);
+	if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
+		qlist_move_all(q, &temp);
+
+		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;
+		}
+		spin_unlock(&quarantine_lock);
+	}
+
+	local_irq_restore(flags);
+}
+
+void 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 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);
+	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 = (READ_ONCE(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;
+	}
+
+	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 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 quarantine_put(),
+	 * nor objects being freed in quarantine_reduce(). on_each_cpu()
+	 * achieves the first goal, while synchronize_srcu() achieves the
+	 * second.
+	 */
+	on_each_cpu(per_cpu_remove_cache, cache, 1);
+
+	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. */
+		spin_unlock_irqrestore(&quarantine_lock, flags);
+		cond_resched();
+		spin_lock_irqsave(&quarantine_lock, flags);
+	}
+	spin_unlock_irqrestore(&quarantine_lock, flags);
+
+	qlist_free_all(&to_free, cache);
+
+	synchronize_srcu(&remove_cache_srcu);
+}