linux-kernel - [ 092/108] slub: Do not hold slub_lock when calling sysfs_slab

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Date:	Fri, 30 Mar 2012 12:58:54 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Sasha Levin <levinsasha928@...il.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>
Subject: [ 092/108] slub: Do not hold slub_lock when calling sysfs_slab_add()

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christoph Lameter <cl@...ux.com>

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@...il.com>
Acked-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Christoph Lameter <cl@...ux.com>
Signed-off-by: Pekka Enberg <penberg@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/slub.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3439,13 +3439,14 @@ struct kmem_cache *kmem_cache_create(con
 		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);


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