From: Yang Shi yang.shi@linux.alibaba.com
mainline inclusion from mainline-v5.5-rc3 commit 42a9a53bb394a1de2247ef78f0b802ae86798122 category: bugfix bugzilla: 47240 CVE: NA
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Since commit 0a432dcbeb32 ("mm: shrinker: make shrinker not depend on memcg kmem"), shrinkers' idr is protected by CONFIG_MEMCG instead of CONFIG_MEMCG_KMEM, so it makes no sense to protect shrinker idr replace with CONFIG_MEMCG_KMEM.
And in the CONFIG_MEMCG && CONFIG_SLOB case, shrinker_idr contains only shrinker, and it is deferred_split_shrinker. But it is never actually called, since idr_replace() is never compiled due to the wrong #ifdef. The deferred_split_shrinker all the time is staying in half-registered state, and it's never called for subordinate mem cgroups.
Link: http://lkml.kernel.org/r/1575486978-45249-1-git-send-email-yang.shi@linux.al... Fixes: 0a432dcbeb32 ("mm: shrinker: make shrinker not depend on memcg kmem") Signed-off-by: Yang Shi yang.shi@linux.alibaba.com Reviewed-by: Kirill Tkhai ktkhai@virtuozzo.com Acked-by: Michal Hocko mhocko@suse.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Shakeel Butt shakeelb@google.com Cc: Roman Gushchin guro@fb.com Cc: stable@vger.kernel.org [5.4+] Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Liu Shixin liushixin2@huawei.com Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.com --- mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c index 099bbd411121..48976d98d5e8 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -421,7 +421,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) { down_write(&shrinker_rwsem); list_add_tail(&shrinker->list, &shrinker_list); -#ifdef CONFIG_MEMCG_KMEM +#ifdef CONFIG_MEMCG if (shrinker->flags & SHRINKER_MEMCG_AWARE) idr_replace(&shrinker_idr, shrinker, shrinker->id); #endif