4 files changed, 82 insertions, 61 deletions

diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
index 8694f7a5d92b..339ba027ade9 100644
--- a/include/linux/slab_def.h
+++ b/include/linux/slab_def.h
@@ -81,7 +81,7 @@ struct kmem_cache {
 #endif
 
 #ifdef CONFIG_SLAB_FREELIST_RANDOM
-        void *random_seq;
+        unsigned int *random_seq;
 #endif
 
         struct kmem_cache_node *node[MAX_NUMNODES];
diff --git a/mm/slab.c b/mm/slab.c
index cc8bbc1e6bc9..763096a247f6 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1236,61 +1236,6 @@ static void __init set_up_node(struct kmem_cache *cachep, int index)
         }
 }
 
-#ifdef CONFIG_SLAB_FREELIST_RANDOM
-static void freelist_randomize(struct rnd_state *state, freelist_idx_t *list,
-                        size_t count)
-{
-        size_t i;
-        unsigned int rand;
-
-        for (i = 0; i < count; i++)
-                list[i] = i;
-
-        /* Fisher-Yates shuffle */
-        for (i = count - 1; i > 0; i--) {
-                rand = prandom_u32_state(state);
-                rand %= (i + 1);
-                swap(list[i], list[rand]);
-        }
-}
-
-/* Create a random sequence per cache */
-static int cache_random_seq_create(struct kmem_cache *cachep, gfp_t gfp)
-{
-        unsigned int seed, count = cachep->num;
-        struct rnd_state state;
-
-        if (count < 2)
-                return 0;
-
-        /* If it fails, we will just use the global lists */
-        cachep->random_seq = kcalloc(count, sizeof(freelist_idx_t), gfp);
-        if (!cachep->random_seq)
-                return -ENOMEM;
-
-        /* Get best entropy at this stage */
-        get_random_bytes_arch(&seed, sizeof(seed));
-        prandom_seed_state(&state, seed);
-
-        freelist_randomize(&state, cachep->random_seq, count);
-        return 0;
-}
-
-/* Destroy the per-cache random freelist sequence */
-static void cache_random_seq_destroy(struct kmem_cache *cachep)
-{
-        kfree(cachep->random_seq);
-        cachep->random_seq = NULL;
-}
-#else
-static inline int cache_random_seq_create(struct kmem_cache *cachep, gfp_t gfp)
-{
-        return 0;
-}
-static inline void cache_random_seq_destroy(struct kmem_cache *cachep) { }
-#endif /* CONFIG_SLAB_FREELIST_RANDOM */
-
-
 /*
  * Initialisation.  Called after the page allocator have been initialised and
  * before smp_init().
@@ -2535,7 +2480,7 @@ static void cache_init_objs_debug(struct kmem_cache *cachep, struct page *page)
 union freelist_init_state {
         struct {
                 unsigned int pos;
-                freelist_idx_t *list;
+                unsigned int *list;
                 unsigned int count;
                 unsigned int rand;
         };
@@ -2554,7 +2499,7 @@ static bool freelist_state_initialize(union freelist_init_state *state,
         unsigned int rand;
 
         /* Use best entropy available to define a random shift */
-        get_random_bytes_arch(&rand, sizeof(rand));
+        rand = get_random_int();
 
         /* Use a random state if the pre-computed list is not available */
         if (!cachep->random_seq) {
@@ -2576,13 +2521,20 @@ static freelist_idx_t next_random_slot(union freelist_init_state *state)
         return (state->list[state->pos++] + state->rand) % state->count;
 }
 
+/* Swap two freelist entries */
+static void swap_free_obj(struct page *page, unsigned int a, unsigned int b)
+{
+        swap(((freelist_idx_t *)page->freelist)[a],
+                ((freelist_idx_t *)page->freelist)[b]);
+}
+
 /*
  * Shuffle the freelist initialization state based on pre-computed lists.
  * return true if the list was successfully shuffled, false otherwise.
  */
 static bool shuffle_freelist(struct kmem_cache *cachep, struct page *page)
 {
-        unsigned int objfreelist = 0, i, count = cachep->num;
+        unsigned int objfreelist = 0, i, rand, count = cachep->num;
         union freelist_init_state state;
         bool precomputed;
 
@@ -2607,7 +2559,15 @@ static bool shuffle_freelist(struct kmem_cache *cachep, struct page *page)
          * Later use a pre-computed list for speed.
          */
         if (!precomputed) {
-                freelist_randomize(&state.rnd_state, page->freelist, count);
+                for (i = 0; i < count; i++)
+                        set_free_obj(page, i, i);
+
+                /* Fisher-Yates shuffle */
+                for (i = count - 1; i > 0; i--) {
+                        rand = prandom_u32_state(&state.rnd_state);
+                        rand %= (i + 1);
+                        swap_free_obj(page, i, rand);
+                }
         } else {
                 for (i = 0; i < count; i++)
                         set_free_obj(page, i, next_random_slot(&state));
@@ -3979,7 +3939,7 @@ static int enable_cpucache(struct kmem_cache *cachep, gfp_t gfp)
         int shared = 0;
         int batchcount = 0;
 
-        err = cache_random_seq_create(cachep, gfp);
+        err = cache_random_seq_create(cachep, cachep->num, gfp);
         if (err)
                 goto end;
 
diff --git a/mm/slab.h b/mm/slab.h
index dedb1a920fb8..5fa8b8f20eb1 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -42,6 +42,7 @@ struct kmem_cache {
 #include <linux/kmemcheck.h>
 #include <linux/kasan.h>
 #include <linux/kmemleak.h>
+#include <linux/random.h>
 
 /*
  * State of the slab allocator.
@@ -464,4 +465,17 @@ int memcg_slab_show(struct seq_file *m, void *p);
 
 void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr);
 
+#ifdef CONFIG_SLAB_FREELIST_RANDOM
+int cache_random_seq_create(struct kmem_cache *cachep, unsigned int count,
+                        gfp_t gfp);
+void cache_random_seq_destroy(struct kmem_cache *cachep);
+#else
+static inline int cache_random_seq_create(struct kmem_cache *cachep,
+                                        unsigned int count, gfp_t gfp)
+{
+        return 0;
+}
+static inline void cache_random_seq_destroy(struct kmem_cache *cachep) { }
+#endif /* CONFIG_SLAB_FREELIST_RANDOM */
+
 #endif /* MM_SLAB_H */
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 82317abb03ed..da88c1588752 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1030,6 +1030,53 @@ void *kmalloc_order_trace(size_t size, gfp_t flags, unsigned int order)
 EXPORT_SYMBOL(kmalloc_order_trace);
 #endif
 
+#ifdef CONFIG_SLAB_FREELIST_RANDOM
+/* Randomize a generic freelist */
+static void freelist_randomize(struct rnd_state *state, unsigned int *list,
+                        size_t count)
+{
+        size_t i;
+        unsigned int rand;
+
+        for (i = 0; i < count; i++)
+                list[i] = i;
+
+        /* Fisher-Yates shuffle */
+        for (i = count - 1; i > 0; i--) {
+                rand = prandom_u32_state(state);
+                rand %= (i + 1);
+                swap(list[i], list[rand]);
+        }
+}
+
+/* Create a random sequence per cache */
+int cache_random_seq_create(struct kmem_cache *cachep, unsigned int count,
+                                    gfp_t gfp)
+{
+        struct rnd_state state;
+
+        if (count < 2 || cachep->random_seq)
+                return 0;
+
+        cachep->random_seq = kcalloc(count, sizeof(unsigned int), gfp);
+        if (!cachep->random_seq)
+                return -ENOMEM;
+
+        /* Get best entropy at this stage of boot */
+        prandom_seed_state(&state, get_random_long());
+
+        freelist_randomize(&state, cachep->random_seq, count);
+        return 0;
+}
+
+/* Destroy the per-cache random freelist sequence */
+void cache_random_seq_destroy(struct kmem_cache *cachep)
+{
+        kfree(cachep->random_seq);
+        cachep->random_seq = NULL;
+}
+#endif /* CONFIG_SLAB_FREELIST_RANDOM */
+
 #ifdef CONFIG_SLABINFO
 
 #ifdef CONFIG_SLAB