On 2021/7/28 17:13, Wang Hai wrote:
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.
So in this case, there is no need to do anything with this large
page in memcg_slab_free_hook(), just skip it.
Fixes: 270c6a71460e ("mm: memcontrol/slab: Use helpers to access slab page's memcg_data")
Signed-off-by: Wang Hai <wanghai38@xxxxxxxxxx>
Reviewed-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
mm/slab.h | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/mm/slab.h b/mm/slab.h
index 67e06637ff2e..247d3f9c21f7 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -339,15 +339,20 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig,
continue;
page = virt_to_head_page(p[i]);
+ if (!s_orig) {
+ if (unlikely(!PageSlab(page))) {
+ BUG_ON(!PageCompound(page));
+ continue;
+ }
+ s = page->slab_cache;
+ } else {
+ s = s_orig;
+ }
+
objcgs = page_objcgs(page);
if (!objcgs)
continue;
- if (!s_orig)
- s = page->slab_cache;
- else
- s = s_orig;
-
off = obj_to_index(s, page, p[i]);
objcg = objcgs[off];
if (!objcg)
