slub: Do not hold slub_lock when calling sysfs_slab_add()

BugLink: http://bugs.launchpad.net/bugs/971808

commit 66c4c35c6bc5a1a452b024cf0364635b28fd94e4 upstream.

sysfs_slab_add() calls various sysfs functions that actually may
end up in userspace doing all sorts of things.

Release the slub_lock after adding the kmem_cache structure to the list.
At that point the address of the kmem_cache is not known so we are
guaranteed exlusive access to the following modifications to the
kmem_cache structure.

If the sysfs_slab_add fails then reacquire the slub_lock to
remove the kmem_cache structure from the list.

Reported-by: Sasha Levin <levinsasha928@gmail.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 0d0901ebaea..10ab2335e2e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3439,13 +3439,14 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size,
                 if (kmem_cache_open(s, n,
                                 size, align, flags, ctor)) {
                         list_add(&s->list, &slab_caches);
+                        up_write(&slub_lock);
                         if (sysfs_slab_add(s)) {
+                                down_write(&slub_lock);
                                 list_del(&s->list);
                                 kfree(n);
                                 kfree(s);
                                 goto err;
                         }
-                        up_write(&slub_lock);
                         return s;
                 }
                 kfree(n);