1 files changed, 44 insertions, 8 deletions

diff --git a/mm/slub.c b/mm/slub.c
index e8b4e31162ca..ddb04576b342 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -34,6 +34,7 @@
 #include <linux/stacktrace.h>
 #include <linux/prefetch.h>
 #include <linux/memcontrol.h>
+#include <linux/random.h>
 
 #include <trace/events/kmem.h>
 
@@ -238,30 +239,62 @@ static inline void stat(const struct kmem_cache *s, enum stat_item si)
  * 			Core slab cache functions
  *******************************************************************/
 
+/*
+ * Returns freelist pointer (ptr). With hardening, this is obfuscated
+ * with an XOR of the address where the pointer is held and a per-cache
+ * random number.
+ */
+static inline void *freelist_ptr(const struct kmem_cache *s, void *ptr,
+				 unsigned long ptr_addr)
+{
+#ifdef CONFIG_SLAB_FREELIST_HARDENED
+	return (void *)((unsigned long)ptr ^ s->random ^ ptr_addr);
+#else
+	return ptr;
+#endif
+}
+
+/* Returns the freelist pointer recorded at location ptr_addr. */
+static inline void *freelist_dereference(const struct kmem_cache *s,
+					 void *ptr_addr)
+{
+	return freelist_ptr(s, (void *)*(unsigned long *)(ptr_addr),
+			    (unsigned long)ptr_addr);
+}
+
 static inline void *get_freepointer(struct kmem_cache *s, void *object)
 {
-	return *(void **)(object + s->offset);
+	return freelist_dereference(s, object + s->offset);
 }
 
 static void prefetch_freepointer(const struct kmem_cache *s, void *object)
 {
-	prefetch(object + s->offset);
+	if (object)
+		prefetch(freelist_dereference(s, object + s->offset));
 }
 
 static inline void *get_freepointer_safe(struct kmem_cache *s, void *object)
 {
+	unsigned long freepointer_addr;
 	void *p;
 
 	if (!debug_pagealloc_enabled())
 		return get_freepointer(s, object);
 
-	probe_kernel_read(&p, (void **)(object + s->offset), sizeof(p));
-	return p;
+	freepointer_addr = (unsigned long)object + s->offset;
+	probe_kernel_read(&p, (void **)freepointer_addr, sizeof(p));
+	return freelist_ptr(s, p, freepointer_addr);
 }
 
 static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp)
 {
-	*(void **)(object + s->offset) = fp;
+	unsigned long freeptr_addr = (unsigned long)object + s->offset;
+
+#ifdef CONFIG_SLAB_FREELIST_HARDENED
+	BUG_ON(object == fp); /* naive detection of double free or corruption */
+#endif
+
+	*(void **)freeptr_addr = freelist_ptr(s, fp, freeptr_addr);
 }
 
 /* Loop over all objects in a slab */
@@ -3358,8 +3391,8 @@ static void free_kmem_cache_nodes(struct kmem_cache *s)
 	struct kmem_cache_node *n;
 
 	for_each_kmem_cache_node(s, node, n) {
-		kmem_cache_free(kmem_cache_node, n);
 		s->node[node] = NULL;
+		kmem_cache_free(kmem_cache_node, n);
 	}
 }
 
@@ -3389,8 +3422,8 @@ static int init_kmem_cache_nodes(struct kmem_cache *s)
 			return 0;
 		}
 
-		s->node[node] = n;
 		init_kmem_cache_node(n);
+		s->node[node] = n;
 	}
 	return 1;
 }
@@ -3563,6 +3596,9 @@ static int kmem_cache_open(struct kmem_cache *s, unsigned long flags)
 {
 	s->flags = kmem_cache_flags(s->size, flags, s->name, s->ctor);
 	s->reserved = 0;
+#ifdef CONFIG_SLAB_FREELIST_HARDENED
+	s->random = get_random_long();
+#endif
 
 	if (need_reserve_slab_rcu && (s->flags & SLAB_TYPESAFE_BY_RCU))
 		s->reserved = sizeof(struct rcu_head);
@@ -5423,7 +5459,7 @@ static struct attribute *slab_attrs[] = {
 	NULL
 };
 
-static struct attribute_group slab_attr_group = {
+static const struct attribute_group slab_attr_group = {
 	.attrs = slab_attrs,
 };