linux-kernel - Re: [QUESTION] Question about 'epoll: do not insert into poll queues until all,sanity checks are done'

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Message-ID: <5e19830c-8653-e575-78db-ddcfc76839cc@huawei.com>
Date:   Fri, 28 Jan 2022 16:41:25 +0800
From:   Zhang Yi <yi.zhang@...wei.com>
To:     yebin <yebin10@...wei.com>, <viro@...iv.linux.org.uk>
CC:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        <linux-fsdevel@...r.kernel.org>, <yeweihua4@...wei.com>
Subject: Re: [QUESTION] Question about 'epoll: do not insert into poll queues
 until all,sanity checks are done'

+CC linux-kernel@...r.kernel.org and linux-fsdevel@...r.kernel.org mail list.

On 2022/1/28 10:09, yebin wrote:
> Hi, AL.
> I'm sorry to bother you.
> Now there is a CVE(CVE-2021-39634) which discription is "In fs/eventpoll.c, there is a possible use after free".
> The information disclosed now shows that fix patch is "epoll: do not insert into poll queues until all
> sanity checks are done" which you submitted.
> According to the patch modification, I reverse analyze how to generate use-after-free .After analysis for several days,
> I tried to reproduce it, but I didn't find any use-after-free.
> Do you have any suggestions for the use-after-free described by CVE-2021-39634?