linux-kernel - Re: double call identical release when there is a race hitting

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] [day] [month] [year] [list]

Message-ID: <593762FF.10705@huawei.com>
Date:   Wed, 7 Jun 2017 10:20:47 +0800
From:   zhong jiang <zhongjiang@...wei.com>
To:     Oleg Nesterov <oleg@...hat.com>
CC:     Michal Hocko <mhocko@...nel.org>, Vlastimil Babka <vbabka@...e.cz>,
        "David Rientjes" <rientjes@...gle.com>,
        Hugh Dickins <hughd@...gle.com>,
        "Linux Memory Management List" <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Xishi Qiu <qiuxishi@...wei.com>
Subject: Re: double call identical release when there is a race hitting

On 2017/6/6 23:56, Oleg Nesterov wrote:
> I can't answer authoritatively, but
>
> On 06/06, zhong jiang wrote:
>> Hi
>>
>> when I review the code, I find the following scenario will lead to a race ,
>> but I am not sure whether the real issue will hit or not.
>>
>> cpu1                                                                      cpu2
>> exit_mmap                                               mmu_notifier_unregister
>>    __mmu_notifier_release                                 srcu_read_lock
>>             srcu_read_lock
>>             mm->ops->release(mn, mm)                 mm->ops->release(mn,mm)
>>            srcu_read_unlock                                         srcu_read_unlock
>>
>>
>> obviously,  the specified mm will call identical release function when
>> the related condition satisfy.  is it right?
> I think you are right, this is possible, perhaps the comments should mention
> this explicitly.
>
> See the changelog in d34883d4e35c0a994e91dd847a82b4c9e0c31d83 "mm: mmu_notifier:
> re-fix freed page still mapped in secondary MMU":
>
> 	"multiple ->release() callouts", we needn't care it too much ...
>
> Oleg.
>
>
> .
>
Thank you for clarification.
 yes,  I see that the author admit that this is a issue.   The patch describe that it is really rare.
 Anyway, this issue should be fixed in a separate patch.

but so far  the issue still exist unfortunately.

Regards
zhongjiang