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From: Michal Hocko <mhocko@kernel.org>
To: Miles Chen <miles.chen@mediatek.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	cgroups@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org,
	wsd_upstream@mediatek.com
Subject: Re: [PATCH v2] mm: memcontrol: fix use after free in mem_cgroup_iter()
Date: Mon, 29 Jul 2019 08:25:00 +0200	[thread overview]
Message-ID: <20190729062500.GB9330@dhcp22.suse.cz> (raw)
In-Reply-To: <1564184878.19817.5.camel@mtkswgap22>

On Sat 27-07-19 07:47:58, Miles Chen wrote:
> On Fri, 2019-07-26 at 14:55 +0200, Michal Hocko wrote:
[...]
> > > I am sorry, I didn't get to comment an earlier version but I am
> > > wondering whether it makes more sense to do and explicit invalidation.
> > > 
> 
> I think we should keep the original v2 version, the reason is the 
> !use_hierarchy does not imply we can reach root_mem_cgroup:
> 
> cd /sys/fs/cgroup/memory/0
> mkdir 1
> cd /sys/fs/cgroup/memory/0/1
> echo 1 > memory.use_hierarchy // only 1 and its children has
> use_hierarchy set
> mkdir 2
> 
> rmdir 2 // parent_mem_cgroup(2) goes up to 1

You are right I have missed this case. I am not sure anybody is using
layout like that but your fix is more robust and catches that case as
well.

Acked-by: Michal Hocko <mhocko@suse.com>
-- 
Michal Hocko
SUSE Labs

  parent reply	other threads:[~2019-07-29  6:25 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-26  2:12 [PATCH v2] mm: memcontrol: fix use after free in mem_cgroup_iter() Miles Chen
2019-07-26 10:20 ` Miles Chen
2019-07-26 12:49 ` Michal Hocko
2019-07-26 12:55   ` Michal Hocko
2019-07-26 23:47     ` Miles Chen
2019-07-27  6:00       ` Miles Chen
2019-07-29  6:25       ` Michal Hocko [this message]
2019-07-29 16:06 ` Johannes Weiner
2019-07-30  1:48   ` Miles Chen

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