[PATCH 5.10.y 11/11] mm/memcg: fix NULL pointer dereference in memcg_slab_free_hook()

From: Chen Huang <chenhuang5@huawei.com>
To: Roman Gushchin <guro@fb.com>,
	Muchun Song <songmuchun@bytedance.com>,
	"Wang Hai" <wanghai38@huawei.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
	<stable@vger.kernel.org>, Chen Huang <chenhuang5@huawei.com>,
	"Christoph Lameter" <cl@linux.com>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 5.10.y 11/11] mm/memcg: fix NULL pointer dereference in memcg_slab_free_hook()
Date: Mon, 16 Aug 2021 07:21:47 +0000	[thread overview]
Message-ID: <20210816072147.3481782-12-chenhuang5@huawei.com> (raw)
In-Reply-To: <20210816072147.3481782-1-chenhuang5@huawei.com>

From: Wang Hai <wanghai38@huawei.com>

When I use kfree_rcu() to free a large memory allocated by kmalloc_node(),
the following dump occurs.

  BUG: kernel NULL pointer dereference, address: 0000000000000020
  [...]
  Oops: 0000 [#1] SMP
  [...]
  Workqueue: events kfree_rcu_work
  RIP: 0010:__obj_to_index include/linux/slub_def.h:182 [inline]
  RIP: 0010:obj_to_index include/linux/slub_def.h:191 [inline]
  RIP: 0010:memcg_slab_free_hook+0x120/0x260 mm/slab.h:363
  [...]
  Call Trace:
    kmem_cache_free_bulk+0x58/0x630 mm/slub.c:3293
    kfree_bulk include/linux/slab.h:413 [inline]
    kfree_rcu_work+0x1ab/0x200 kernel/rcu/tree.c:3300
    process_one_work+0x207/0x530 kernel/workqueue.c:2276
    worker_thread+0x320/0x610 kernel/workqueue.c:2422
    kthread+0x13d/0x160 kernel/kthread.c:313
    ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

When kmalloc_node() a large memory, page is allocated, not slab, so when
freeing memory via kfree_rcu(), this large memory should not be used by
memcg_slab_free_hook(), because memcg_slab_free_hook() is is used for
slab.

Using page_objcgs_check() instead of page_objcgs() in
memcg_slab_free_hook() to fix this bug.

Link: https://lkml.kernel.org/r/20210728145655.274476-1-wanghai38@huawei.com
Fixes: 270c6a71460e ("mm: memcontrol/slab: Use helpers to access slab page's memcg_data")
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Chen Huang <chenhuang5@huawei.com>
---
 mm/slab.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slab.h b/mm/slab.h
index 571757eb4a8f..9759992c720c 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -349,7 +349,7 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig,
 			continue;
 
 		page = virt_to_head_page(p[i]);
-		objcgs = page_objcgs(page);
+		objcgs = page_objcgs_check(page);
 		if (!objcgs)
 			continue;
 
-- 
2.18.0.huawei.25


