[PATCH 4.14 308/496] mm, slab: memcg_link the SLABs kmem_cache

[Greg Kroah-Hartman]

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

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

From: Shakeel Butt <shakeelb@xxxxxxxxxx>

[ Upstream commit 880cd276dff17ea29e9a8404275c9502b265afa7 ]

All the root caches are linked into slab_root_caches which was
introduced by the commit 510ded33e075 ("slab: implement slab_root_caches
list") but it missed to add the SLAB's kmem_cache.

While experimenting with opt-in/opt-out kmem accounting, I noticed
system crashes due to NULL dereference inside cache_from_memcg_idx()
while deferencing kmem_cache.memcg_params.memcg_caches.  The upstream
clean kernel will not see these crashes but SLAB should be consistent
with SLUB which does linked its boot caches (kmem_cache_node and
kmem_cache) into slab_root_caches.

Link: http://lkml.kernel.org/r/20180319210020.60289-1-shakeelb@xxxxxxxxxx
Fixes: 510ded33e075c ("slab: implement slab_root_caches list")
Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Greg Thelen <gthelen@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 mm/slab.c |    1 +
 1 file changed, 1 insertion(+)

--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1283,6 +1283,7 @@ void __init kmem_cache_init(void)
 				  nr_node_ids * sizeof(struct kmem_cache_node *),
 				  SLAB_HWCACHE_ALIGN);
 	list_add(&kmem_cache->list, &slab_caches);
+	memcg_link_cache(kmem_cache);
 	slab_state = PARTIAL;
 
 	/*