linux-kernel - Re: [PATCH v2] mm: memcontrol: fix use after free in mem_cgroup

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <20190729062500.GB9330@dhcp22.suse.cz>
Date:   Mon, 29 Jul 2019 08:25:00 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Miles Chen <miles.chen@...iatek.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        wsd_upstream@...iatek.com
Subject: Re: [PATCH v2] mm: memcontrol: fix use after free in
 mem_cgroup_iter()

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@...e.com>
-- 
Michal Hocko
SUSE Labs