From: Christoph Lameter <cl@linux.com>
Date: Tue, 17 Jan 2012 15:27:31 +0000 (-0600)
Subject: slub: Do not hold slub_lock when calling sysfs_slab_add()
X-Git-Tag: firefly_0821_release~7541^2~1460
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=295706896259f338b1c69e0b3a293c77beb372c0;p=firefly-linux-kernel-4.4.55.git

slub: Do not hold slub_lock when calling sysfs_slab_add()

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>
---

diff --git a/mm/slub.c b/mm/slub.c
index 0d0901ebaea2..10ab2335e2ea 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);