[ 155/175] slub: Do not hold slub_lock when calling sysfs_slab_add()

From: Greg KH
Date: Fri Mar 30 2012 - 17:32:18 EST

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


From: Christoph Lameter <cl@xxxxxxxxx>

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@xxxxxxxxx>
Acked-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3929,13 +3929,14 @@ 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);
goto err;
- up_write(&slub_lock);
return s;

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