netdev - Re: [PATCH bpf-next 13/15] mm, memcg: Add new helper get_obj_cgroup_from

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YvUrXLJF6qrGOdjP@P9FQF9L96D.corp.robot.car>
Date:   Thu, 11 Aug 2022 09:16:28 -0700
From:   Roman Gushchin <roman.gushchin@...ux.dev>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, hannes@...xchg.org,
        mhocko@...nel.org, shakeelb@...gle.com, songmuchun@...edance.com,
        akpm@...ux-foundation.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH bpf-next 13/15] mm, memcg: Add new helper
 get_obj_cgroup_from_cgroup

On Wed, Aug 10, 2022 at 03:18:38PM +0000, Yafang Shao wrote:
> Introduce new helper get_obj_cgroup_from_cgroup() to get obj_cgroup from
> a specific cgroup.
> 
> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> ---
>  include/linux/memcontrol.h |  1 +
>  mm/memcontrol.c            | 41 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 42 insertions(+)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 2f0a611..901a921 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1713,6 +1713,7 @@ static inline void set_shrinker_bit(struct mem_cgroup *memcg,
>  int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order);
>  void __memcg_kmem_uncharge_page(struct page *page, int order);
>  
> +struct obj_cgroup *get_obj_cgroup_from_cgroup(struct cgroup *cgrp);
>  struct obj_cgroup *get_obj_cgroup_from_current(void);
>  struct obj_cgroup *get_obj_cgroup_from_page(struct page *page);
>  
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 618c366..762cffa 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2908,6 +2908,47 @@ static struct obj_cgroup *__get_obj_cgroup_from_memcg(struct mem_cgroup *memcg)
>  	return objcg;
>  }
>  
> +static struct obj_cgroup *get_obj_cgroup_from_memcg(struct mem_cgroup *memcg)
> +{
> +	struct obj_cgroup *objcg;
> +
> +	if (memcg_kmem_bypass())
> +		return NULL;
> +
> +	rcu_read_lock();
> +	objcg = __get_obj_cgroup_from_memcg(memcg);
> +	rcu_read_unlock();
> +	return objcg;

This code doesn't make sense to me. What does rcu read lock protect here?