SLUB: Fix merged slab cache names

As explained by Linus "I'm Proud to be an American" Torvalds:

  Looking at the merging code, I actually think it's totally
  buggy. If you have something like this:

   - load module A: create slab cache A

   - load module B: create slab cache B that can merge with A

   - unload module A

   - "cat /proc/slabinfo": BOOM. Oops.

  exactly because the name is not handled correctly, and you'll have
  module B holding open a slab cache that has a name pointer that points
  to module A that no longer exists.

This patch fixes the problem by using kstrdup() to allocate dynamic memory for
->name of "struct kmem_cache" as suggested by Christoph Lameter.

Acked-by: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

Conflicts:

	mm/slub.c

1 files changed, 20 insertions, 1 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 05674aac9294..42ce17304275 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -209,6 +209,7 @@ static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
                                                         { return 0; }
 static inline void sysfs_slab_remove(struct kmem_cache *s)
 {
+        kfree(s->name);
         kfree(s);
 }
 
@@ -3169,6 +3170,16 @@ void __init kmem_cache_init(void)
         slab_state = UP;
 
         /* Provide the correct kmalloc names now that the caches are up */
+        if (KMALLOC_MIN_SIZE <= 32) {
+                kmalloc_caches[1]->name = kstrdup(kmalloc_caches[1]->name, GFP_NOWAIT);
+                BUG_ON(!kmalloc_caches[1]->name);
+        }
+
+        if (KMALLOC_MIN_SIZE <= 64) {
+                kmalloc_caches[2]->name = kstrdup(kmalloc_caches[2]->name, GFP_NOWAIT);
+                BUG_ON(!kmalloc_caches[2]->name);
+        }
+
         for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
                 char *s = kasprintf(GFP_NOWAIT, "kmalloc-%d", 1 << i);
 
@@ -3271,6 +3282,7 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size,
                 size_t align, unsigned long flags, void (*ctor)(void *))
 {
         struct kmem_cache *s;
+        char *n;
 
         if (WARN_ON(!name))
                 return NULL;
@@ -3294,19 +3306,25 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size,
                 return s;
         }
 
+        n = kstrdup(name, GFP_KERNEL);
+        if (!n)
+                goto err;
+
         s = kmalloc(kmem_size, GFP_KERNEL);
         if (s) {
-                if (kmem_cache_open(s, name,
+                if (kmem_cache_open(s, n,
                                 size, align, flags, ctor)) {
                         list_add(&s->list, &slab_caches);
                         if (sysfs_slab_add(s)) {
                                 list_del(&s->list);
+                                kfree(n);
                                 kfree(s);
                                 goto err;
                         }
                         up_write(&slub_lock);
                         return s;
                 }
+                kfree(n);
                 kfree(s);
         }
         up_write(&slub_lock);
@@ -4439,6 +4457,7 @@ static void kmem_cache_release(struct kobject *kobj)
 {
         struct kmem_cache *s = to_slab(kobj);
 
+        kfree(s->name);
         kfree(s);
 }