From: Roman Gushchin <guro@fb.com>
To: Muchun Song <songmuchun@bytedance.com>
Cc: <hannes@cmpxchg.org>, <mhocko@kernel.org>,
<akpm@linux-foundation.org>, <shakeelb@google.com>,
<vdavydov.dev@gmail.com>, <linux-kernel@vger.kernel.org>,
<linux-mm@kvack.org>, <duanxiongchun@bytedance.com>
Subject: Re: [PATCH v5 1/7] mm: memcontrol: slab: fix obtain a reference to a freeing memcg
Date: Mon, 22 Mar 2021 11:17:15 -0700 [thread overview]
Message-ID: <YFjfK+F3dVgOABUl@carbon.dhcp.thefacebook.com> (raw)
In-Reply-To: <20210319163821.20704-2-songmuchun@bytedance.com>
On Sat, Mar 20, 2021 at 12:38:14AM +0800, Muchun Song wrote:
> The rcu_read_lock/unlock only can guarantee that the memcg will not be
> freed, but it cannot guarantee the success of css_get (which is in the
> refill_stock when cached memcg changed) to memcg.
>
> rcu_read_lock()
> memcg = obj_cgroup_memcg(old)
> __memcg_kmem_uncharge(memcg)
> refill_stock(memcg)
> if (stock->cached != memcg)
> // css_get can change the ref counter from 0 back to 1.
> css_get(&memcg->css)
> rcu_read_unlock()
>
> This fix is very like the commit:
>
> eefbfa7fd678 ("mm: memcg/slab: fix use after free in obj_cgroup_charge")
>
> Fix this by holding a reference to the memcg which is passed to the
> __memcg_kmem_uncharge() before calling __memcg_kmem_uncharge().
>
> Fixes: 3de7d4f25a74 ("mm: memcg/slab: optimize objcg stock draining")
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Roman Gushchin <guro@fb.com>
Thanks!
next prev parent reply other threads:[~2021-03-22 18:17 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-19 16:38 [PATCH v5 0/7] Use obj_cgroup APIs to charge kmem pages Muchun Song
2021-03-19 16:38 ` [PATCH v5 1/7] mm: memcontrol: slab: fix obtain a reference to a freeing memcg Muchun Song
2021-03-19 18:26 ` Shakeel Butt
2021-03-22 14:46 ` Johannes Weiner
2021-03-23 9:18 ` [External] " Muchun Song
2021-03-22 18:17 ` Roman Gushchin [this message]
2021-03-19 16:38 ` [PATCH v5 2/7] mm: memcontrol: introduce obj_cgroup_{un}charge_pages Muchun Song
2021-03-19 16:38 ` [PATCH v5 3/7] mm: memcontrol: directly access page->memcg_data in mm/page_alloc.c Muchun Song
2021-03-19 16:38 ` [PATCH v5 4/7] mm: memcontrol: change ug->dummy_page only if memcg changed Muchun Song
2021-03-19 16:38 ` [PATCH v5 5/7] mm: memcontrol: use obj_cgroup APIs to charge kmem pages Muchun Song
2021-03-19 18:27 ` Shakeel Butt
2021-03-22 18:13 ` Roman Gushchin
2021-03-19 16:38 ` [PATCH v5 6/7] mm: memcontrol: inline __memcg_kmem_{un}charge() into obj_cgroup_{un}charge_pages() Muchun Song
2021-03-19 18:41 ` Shakeel Butt
2021-03-22 14:34 ` Johannes Weiner
2021-03-22 18:14 ` Roman Gushchin
2021-03-19 16:38 ` [PATCH v5 7/7] mm: memcontrol: move PageMemcgKmem to the scope of CONFIG_MEMCG_KMEM Muchun Song
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