linux-kernel - [PATCH 5.13 013/104] mm/memcg: fix NULL pointer dereference in memcg_slab_free

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Date:   Mon,  2 Aug 2021 15:44:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Wang Hai <wanghai38@...wei.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Michal Hocko <mhocko@...e.com>, Roman Gushchin <guro@...com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Muchun Song <songmuchun@...edance.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Johannes Weiner <hannes@...xchg.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.13 013/104] mm/memcg: fix NULL pointer dereference in memcg_slab_free_hook()

From: Wang Hai <wanghai38@...wei.com>

commit 121dffe20b141c9b27f39d49b15882469cbebae7 upstream.

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@...wei.com>
Reviewed-by: Shakeel Butt <shakeelb@...gle.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Acked-by: Roman Gushchin <guro@...com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@...wei.com>
Reviewed-by: Muchun Song <songmuchun@...edance.com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Pekka Enberg <penberg@...nel.org>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 mm/slab.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/slab.h
+++ b/mm/slab.h
@@ -350,7 +350,7 @@ static inline void memcg_slab_free_hook(
 			continue;
 
 		page = virt_to_head_page(p[i]);
-		objcgs = page_objcgs(page);
+		objcgs = page_objcgs_check(page);
 		if (!objcgs)
 			continue;