kmemleak: Add the slab memory allocation/freeing hooks

This patch adds the callbacks to kmemleak_(alloc|free) functions from
the slab allocator. The patch also adds the SLAB_NOLEAKTRACE flag to
avoid recursive calls to kmemleak when it allocates its own data
structures.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Pekka Enberg <penberg@cs.helsinki.fi>

include/linux/slab.h

@@ -62,6 +62,8 @@
 # define SLAB_DEBUG_OBJECTS	0x00000000UL
 #endif
 
+#define SLAB_NOLEAKTRACE	0x00800000UL	/* Avoid kmemleak tracing */
+
 /* The following flags affect the page allocator grouping pages by mobility */
 #define SLAB_RECLAIM_ACCOUNT	0x00020000UL		/* Objects are reclaimable */
 #define SLAB_TEMPORARY		SLAB_RECLAIM_ACCOUNT	/* Objects are short-lived */

mm/slab.c

@@ -107,6 +107,7 @@
 #include	<linux/string.h>
 #include	<linux/uaccess.h>
 #include	<linux/nodemask.h>
+#include	<linux/kmemleak.h>
 #include	<linux/mempolicy.h>
 #include	<linux/mutex.h>
 #include	<linux/fault-inject.h>
@@ -178,13 +179,13 @@
 			 SLAB_STORE_USER | \
 			 SLAB_RECLAIM_ACCOUNT | SLAB_PANIC | \
 			 SLAB_DESTROY_BY_RCU | SLAB_MEM_SPREAD | \
-			 SLAB_DEBUG_OBJECTS)
+			 SLAB_DEBUG_OBJECTS | SLAB_NOLEAKTRACE)
 #else
 # define CREATE_MASK	(SLAB_HWCACHE_ALIGN | \
 			 SLAB_CACHE_DMA | \
 			 SLAB_RECLAIM_ACCOUNT | SLAB_PANIC | \
 			 SLAB_DESTROY_BY_RCU | SLAB_MEM_SPREAD | \
-			 SLAB_DEBUG_OBJECTS)
+			 SLAB_DEBUG_OBJECTS | SLAB_NOLEAKTRACE)
 #endif
 
 /*
@@ -964,6 +965,14 @@ static struct array_cache *alloc_arraycache(int node, int entries,
 	struct array_cache *nc = NULL;
 
 	nc = kmalloc_node(memsize, GFP_KERNEL, node);
+	/*
+	 * The array_cache structures contain pointers to free object.
+	 * However, when such objects are allocated or transfered to another
+	 * cache the pointers are not cleared and they could be counted as
+	 * valid references during a kmemleak scan. Therefore, kmemleak must
+	 * not scan such objects.
+	 */
+	kmemleak_no_scan(nc);
 	if (nc) {
 		nc->avail = 0;
 		nc->limit = entries;
@@ -2621,6 +2630,14 @@ static struct slab *alloc_slabmgmt(struct kmem_cache *cachep, void *objp,
 		/* Slab management obj is off-slab. */
 		slabp = kmem_cache_alloc_node(cachep->slabp_cache,
 					      local_flags, nodeid);
+		/*
+		 * If the first object in the slab is leaked (it's allocated
+		 * but no one has a reference to it), we want to make sure
+		 * kmemleak does not treat the ->s_mem pointer as a reference
+		 * to the object. Otherwise we will not report the leak.
+		 */
+		kmemleak_scan_area(slabp, offsetof(struct slab, list),
+				   sizeof(struct list_head), local_flags);
 		if (!slabp)
 			return NULL;
 	} else {
@@ -3141,6 +3158,12 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
 		STATS_INC_ALLOCMISS(cachep);
 		objp = cache_alloc_refill(cachep, flags);
 	}
+	/*
+	 * To avoid a false negative, if an object that is in one of the
+	 * per-CPU caches is leaked, we need to make sure kmemleak doesn't
+	 * treat the array pointers as a reference to the object.
+	 */
+	kmemleak_erase(&ac->entry[ac->avail]);
 	return objp;
 }
 
@@ -3360,6 +3383,8 @@ __cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
   out:
 	local_irq_restore(save_flags);
 	ptr = cache_alloc_debugcheck_after(cachep, flags, ptr, caller);
+	kmemleak_alloc_recursive(ptr, obj_size(cachep), 1, cachep->flags,
+				 flags);
 
 	if (unlikely((flags & __GFP_ZERO) && ptr))
 		memset(ptr, 0, obj_size(cachep));
@@ -3415,6 +3440,8 @@ __cache_alloc(struct kmem_cache *cachep, gfp_t flags, void *caller)
 	objp = __do_cache_alloc(cachep, flags);
 	local_irq_restore(save_flags);
 	objp = cache_alloc_debugcheck_after(cachep, flags, objp, caller);
+	kmemleak_alloc_recursive(objp, obj_size(cachep), 1, cachep->flags,
+				 flags);
 	prefetchw(objp);
 
 	if (unlikely((flags & __GFP_ZERO) && objp))
@@ -3530,6 +3557,7 @@ static inline void __cache_free(struct kmem_cache *cachep, void *objp)
 	struct array_cache *ac = cpu_cache_get(cachep);
 
 	check_irq_off();
+	kmemleak_free_recursive(objp, cachep->flags);
 	objp = cache_free_debugcheck(cachep, objp, __builtin_return_address(0));
 
 	/*