5 files changed, 361 insertions, 10 deletions

diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
index 131daadf40e4..1548749a3d45 100644
--- a/mm/kasan/Makefile
+++ b/mm/kasan/Makefile
@@ -8,3 +8,4 @@ CFLAGS_REMOVE_kasan.o = -pg
 CFLAGS_kasan.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
 
 obj-y := kasan.o report.o kasan_init.o
+obj-$(CONFIG_SLAB) += quarantine.o
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 38f1dd79acdb..8df666bb23be 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -388,6 +388,16 @@ void kasan_cache_create(struct kmem_cache *cache, size_t *size,
 }
 #endif
 
+void kasan_cache_shrink(struct kmem_cache *cache)
+{
+	quarantine_remove_cache(cache);
+}
+
+void kasan_cache_destroy(struct kmem_cache *cache)
+{
+	quarantine_remove_cache(cache);
+}
+
 void kasan_poison_slab(struct page *page)
 {
 	kasan_poison_shadow(page_address(page),
@@ -482,7 +492,7 @@ void kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
 	kasan_kmalloc(cache, object, cache->object_size, flags);
 }
 
-void kasan_slab_free(struct kmem_cache *cache, void *object)
+void kasan_poison_slab_free(struct kmem_cache *cache, void *object)
 {
 	unsigned long size = cache->object_size;
 	unsigned long rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
@@ -491,18 +501,43 @@ void kasan_slab_free(struct kmem_cache *cache, void *object)
 	if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
 		return;
 
+	kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
+}
+
+bool kasan_slab_free(struct kmem_cache *cache, void *object)
+{
 #ifdef CONFIG_SLAB
-	if (cache->flags & SLAB_KASAN) {
-		struct kasan_free_meta *free_info =
-			get_free_info(cache, object);
+	/* RCU slabs could be legally used after free within the RCU period */
+	if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
+		return false;
+
+	if (likely(cache->flags & SLAB_KASAN)) {
 		struct kasan_alloc_meta *alloc_info =
 			get_alloc_info(cache, object);
-		alloc_info->state = KASAN_STATE_FREE;
-		set_track(&free_info->track, GFP_NOWAIT);
+		struct kasan_free_meta *free_info =
+			get_free_info(cache, object);
+
+		switch (alloc_info->state) {
+		case KASAN_STATE_ALLOC:
+			alloc_info->state = KASAN_STATE_QUARANTINE;
+			quarantine_put(free_info, cache);
+			set_track(&free_info->track, GFP_NOWAIT);
+			kasan_poison_slab_free(cache, object);
+			return true;
+		case KASAN_STATE_QUARANTINE:
+		case KASAN_STATE_FREE:
+			pr_err("Double free");
+			dump_stack();
+			break;
+		default:
+			break;
+		}
 	}
+	return false;
+#else
+	kasan_poison_slab_free(cache, object);
+	return false;
 #endif
-
-	kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
 }
 
 void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
@@ -511,6 +546,9 @@ void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
 	unsigned long redzone_start;
 	unsigned long redzone_end;
 
+	if (flags & __GFP_RECLAIM)
+		quarantine_reduce();
+
 	if (unlikely(object == NULL))
 		return;
 
@@ -541,6 +579,9 @@ void kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
 	unsigned long redzone_start;
 	unsigned long redzone_end;
 
+	if (flags & __GFP_RECLAIM)
+		quarantine_reduce();
+
 	if (unlikely(ptr == NULL))
 		return;
 
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 30a2f0ba0e09..7f7ac51d7faf 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -62,6 +62,7 @@ struct kasan_global {
 enum kasan_state {
 	KASAN_STATE_INIT,
 	KASAN_STATE_ALLOC,
+	KASAN_STATE_QUARANTINE,
 	KASAN_STATE_FREE
 };
 
@@ -79,9 +80,14 @@ struct kasan_alloc_meta {
 	u32 reserved;
 };
 
+struct qlist_node {
+	struct qlist_node *next;
+};
 struct kasan_free_meta {
-	/* Allocator freelist pointer, unused by KASAN. */
-	void **freelist;
+	/* This field is used while the object is in the quarantine.
+	 * Otherwise it might be used for the allocator freelist.
+	 */
+	struct qlist_node quarantine_link;
 	struct kasan_track track;
 };
 
@@ -105,4 +111,15 @@ static inline bool kasan_report_enabled(void)
 void kasan_report(unsigned long addr, size_t size,
 		bool is_write, unsigned long ip);
 
+#ifdef CONFIG_SLAB
+void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache);
+void quarantine_reduce(void);
+void quarantine_remove_cache(struct kmem_cache *cache);
+#else
+static inline void quarantine_put(struct kasan_free_meta *info,
+				struct kmem_cache *cache) { }
+static inline void quarantine_reduce(void) { }
+static inline void quarantine_remove_cache(struct kmem_cache *cache) { }
+#endif
+
 #endif
diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
new file mode 100644
index 000000000000..4973505a9bdd
--- /dev/null
+++ b/mm/kasan/quarantine.c
@@ -0,0 +1,291 @@
+/*
+ * 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);
+	struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
+	unsigned long flags;
+
+	local_irq_save(flags);
+	alloc_info->state = KASAN_STATE_FREE;
+	___cache_free(cache, object, _THIS_IP_);
+	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;
+	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;
+	new_quarantine_size -= QUARANTINE_PERCPU_SIZE * num_online_cpus();
+	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 *prev = NULL, *curr;
+
+	if (unlikely(qlist_empty(from)))
+		return;
+
+	curr = from->head;
+	while (curr) {
+		struct qlist_node *qlink = curr;
+		struct kmem_cache *obj_cache = qlink_to_cache(qlink);
+
+		if (obj_cache == cache) {
+			if (unlikely(from->head == qlink)) {
+				from->head = curr->next;
+				prev = curr;
+			} else
+				prev->next = curr->next;
+			if (unlikely(from->tail == qlink))
+				from->tail = curr->next;
+			from->bytes -= cache->size;
+			qlist_put(to, qlink, cache->size);
+		} else {
+			prev = curr;
+		}
+		curr = 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);
+}
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 60869a5a0124..b3c122ddd454 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -151,6 +151,7 @@ static void object_err(struct kmem_cache *cache, struct page *page,
 		print_track(&alloc_info->track);
 		break;
 	case KASAN_STATE_FREE:
+	case KASAN_STATE_QUARANTINE:
 		pr_err("Object freed, allocated with size %u bytes\n",
 		       alloc_info->alloc_size);
 		free_info = get_free_info(cache, object);