[kernel-hardening] Re: kmem_cache_attr (was Re: [PATCH 04/36] usercopy: Prepare for usercopy whitelisting)

[Christopher Lameter <cl@linux.com>]

Draft patch of how the data structs could change. kmem_cache_attr is read
only.

Index: linux/include/linux/slab.h
===================================================================
--- linux.orig/include/linux/slab.h
+++ linux/include/linux/slab.h
@@ -135,9 +135,17 @@ struct mem_cgroup;
 void __init kmem_cache_init(void);
 bool slab_is_available(void);

-struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
-			slab_flags_t,
-			void (*)(void *));
+typedef kmem_cache_ctor void (*ctor)(void *);
+
+struct kmem_cache_attr {
+	char name[16];
+	unsigned int size;
+	unsigned int align;
+	slab_flags_t flags;
+	kmem_cache_ctor ctor;
+}
+
+struct kmem_cache *kmem_cache_create(const kmem_cache_attr *);
 void kmem_cache_destroy(struct kmem_cache *);
 int kmem_cache_shrink(struct kmem_cache *);

Index: linux/include/linux/slab_def.h
===================================================================
--- linux.orig/include/linux/slab_def.h
+++ linux/include/linux/slab_def.h
@@ -10,6 +10,7 @@

 struct kmem_cache {
 	struct array_cache __percpu *cpu_cache;
+	struct kmem_cache_attr *attr;

 /* 1) Cache tunables. Protected by slab_mutex */
 	unsigned int batchcount;
@@ -35,14 +36,9 @@ struct kmem_cache {
 	struct kmem_cache *freelist_cache;
 	unsigned int freelist_size;

-	/* constructor func */
-	void (*ctor)(void *obj);
-
 /* 4) cache creation/removal */
-	const char *name;
 	struct list_head list;
 	int refcount;
-	int object_size;
 	int align;

 /* 5) statistics */
Index: linux/include/linux/slub_def.h
===================================================================
--- linux.orig/include/linux/slub_def.h
+++ linux/include/linux/slub_def.h
@@ -83,9 +83,9 @@ struct kmem_cache {
 	struct kmem_cache_cpu __percpu *cpu_slab;
 	/* Used for retriving partial slabs etc */
 	slab_flags_t flags;
+	struct kmem_cache_attr *attr;
 	unsigned long min_partial;
 	int size;		/* The size of an object including meta data */
-	int object_size;	/* The size of an object without meta data */
 	int offset;		/* Free pointer offset. */
 #ifdef CONFIG_SLUB_CPU_PARTIAL
 	int cpu_partial;	/* Number of per cpu partial objects to keep around */
@@ -97,12 +97,10 @@ struct kmem_cache {
 	struct kmem_cache_order_objects min;
 	gfp_t allocflags;	/* gfp flags to use on each alloc */
 	int refcount;		/* Refcount for slab cache destroy */
-	void (*ctor)(void *);
 	int inuse;		/* Offset to metadata */
 	int align;		/* Alignment */
 	int reserved;		/* Reserved bytes at the end of slabs */
 	int red_left_pad;	/* Left redzone padding size */
-	const char *name;	/* Name (only for display!) */
 	struct list_head list;	/* List of slab caches */
 #ifdef CONFIG_SYSFS
 	struct kobject kobj;	/* For sysfs */
Index: linux/mm/slab.h
===================================================================
--- linux.orig/mm/slab.h
+++ linux/mm/slab.h
@@ -18,13 +18,11 @@
  * SLUB is no longer needed.
  */
 struct kmem_cache {
-	unsigned int object_size;/* The original size of the object */
+	struct kmem_cache_attr *attr
 	unsigned int size;	/* The aligned/padded/added on size  */
 	unsigned int align;	/* Alignment as calculated */
 	slab_flags_t flags;	/* Active flags on the slab */
-	const char *name;	/* Slab name for sysfs */
 	int refcount;		/* Use counter */
-	void (*ctor)(void *);	/* Called on object slot creation */
 	struct list_head list;	/* List of all slab caches on the system */
 };