The patch titled
Subject: mm/memcg: fix NULL pointer dereference in memcg_slab_free_hook()
has been added to the -mm tree. Its filename is
mm-memcg-fix-null-pointer-dereference-in-memcg_slab_free_hook.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-fix-null-pointer-dereference-in-memcg_slab_free_hook.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-fix-null-pointer-dereference-in-memcg_slab_free_hook.patch
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------------------------------------------------------
From: Wang Hai <wanghai38@xxxxxxxxxx>
Subject: mm/memcg: fix NULL pointer dereference in memcg_slab_free_hook()
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@xxxxxxxxxx
Fixes: 270c6a71460e ("mm: memcontrol/slab: Use helpers to access slab page's memcg_data")
Signed-off-by: Wang Hai <wanghai38@xxxxxxxxxx>
Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slab.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/slab.h~mm-memcg-fix-null-pointer-dereference-in-memcg_slab_free_hook
+++ a/mm/slab.h
@@ -346,7 +346,7 @@ 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;
_
Patches currently in -mm which might be from wanghai38@xxxxxxxxxx are
mm-memcg-fix-null-pointer-dereference-in-memcg_slab_free_hook.patch
