Commit d330076e authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'slab-for-6.0-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab 

Pull slab fix from Vlastimil Babka:

 - A fix from Waiman Long to avoid a theoretical deadlock reported by
   lockdep.

* tag 'slab-for-6.0-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab:
  mm/slab_common: Deleting kobject in kmem_cache_destroy() without holding slab_mutex/cpu_hotplug_lock
parents 2880e1a1 0495e337

mm/slab_common.c

+29 −16
Original line number Diff line number Diff line
@@ -392,6 +392,28 @@ kmem_cache_create(const char *name, unsigned int size, unsigned int align, 
}

EXPORT_SYMBOL(kmem_cache_create);



#ifdef SLAB_SUPPORTS_SYSFS

/*

 * For a given kmem_cache, kmem_cache_destroy() should only be called

 * once or there will be a use-after-free problem. The actual deletion

 * and release of the kobject does not need slab_mutex or cpu_hotplug_lock

 * protection. So they are now done without holding those locks.

 *

 * Note that there will be a slight delay in the deletion of sysfs files

 * if kmem_cache_release() is called indrectly from a work function.

 */

static void kmem_cache_release(struct kmem_cache *s)

{

	sysfs_slab_unlink(s);

	sysfs_slab_release(s);

}

#else

static void kmem_cache_release(struct kmem_cache *s)

{

	slab_kmem_cache_release(s);

}

#endif



static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)

{

	LIST_HEAD(to_destroy);
@@ -418,11 +440,7 @@ static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work) 
	list_for_each_entry_safe(s, s2, &to_destroy, list) {

		debugfs_slab_release(s);

		kfence_shutdown_cache(s);

#ifdef SLAB_SUPPORTS_SYSFS

		sysfs_slab_release(s);

#else

		slab_kmem_cache_release(s);

#endif

		kmem_cache_release(s);

	}

}
@@ -437,20 +455,11 @@ static int shutdown_cache(struct kmem_cache *s) 
	list_del(&s->list);



	if (s->flags & SLAB_TYPESAFE_BY_RCU) {

#ifdef SLAB_SUPPORTS_SYSFS

		sysfs_slab_unlink(s);

#endif

		list_add_tail(&s->list, &slab_caches_to_rcu_destroy);

		schedule_work(&slab_caches_to_rcu_destroy_work);

	} else {

		kfence_shutdown_cache(s);

		debugfs_slab_release(s);

#ifdef SLAB_SUPPORTS_SYSFS

		sysfs_slab_unlink(s);

		sysfs_slab_release(s);

#else

		slab_kmem_cache_release(s);

#endif

	}



	return 0;
@@ -465,14 +474,16 @@ void slab_kmem_cache_release(struct kmem_cache *s) 


void kmem_cache_destroy(struct kmem_cache *s)

{

	int refcnt;



	if (unlikely(!s) || !kasan_check_byte(s))

		return;



	cpus_read_lock();

	mutex_lock(&slab_mutex);



	s->refcount--;

	if (s->refcount)

	refcnt = --s->refcount;

	if (refcnt)

		goto out_unlock;



	WARN(shutdown_cache(s),
@@ -481,6 +492,8 @@ void kmem_cache_destroy(struct kmem_cache *s) 
out_unlock:

	mutex_unlock(&slab_mutex);

	cpus_read_unlock();

	if (!refcnt && !(s->flags & SLAB_TYPESAFE_BY_RCU))

		kmem_cache_release(s);

}

EXPORT_SYMBOL(kmem_cache_destroy);