linux-kernel - Re: [PATCH v3 1/1] mm: fix use-after-free when anon vma name is used after vma is freed

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Message-ID: <YgwHhTN4P5yyZqBz@dhcp22.suse.cz>
Date:   Tue, 15 Feb 2022 21:05:25 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     akpm@...ux-foundation.org, ccross@...gle.com,
        sumit.semwal@...aro.org, dave.hansen@...el.com,
        keescook@...omium.org, willy@...radead.org,
        kirill.shutemov@...ux.intel.com, vbabka@...e.cz,
        hannes@...xchg.org, ebiederm@...ssion.com, brauner@...nel.org,
        legion@...nel.org, ran.xiaokai@....com.cn, sashal@...nel.org,
        chris.hyser@...cle.com, dave@...olabs.net, pcc@...gle.com,
        caoxiaofeng@...ong.com, david@...hat.com, gorcunov@...il.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com,
        syzbot+aa7b3d4b35f9dc46a366@...kaller.appspotmail.com
Subject: Re: [PATCH v3 1/1] mm: fix use-after-free when anon vma name is used
 after vma is freed

One thing I was considering is to check agains ref counte overflo (a
deep process chain with many vmas could grow really high. ref_count
interface doesn't provide any easy way to check for overflows as far as
I could see from a quick glance so I gave up there but the logic would
be really straightforward. We just create a new anon_vma_name with the same
content and use it when duplicating if the usage grow really
(arbitrarily) high.
-- 
Michal Hocko
SUSE Labs