linux-kernel - Re: [PATCH] mm: mmu_notifier: fix inconsistent memory between secondary MMU and host

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]

Date:	Wed, 22 Aug 2012 13:37:59 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Hugh Dickins <hughd@...gle.com>
CC:	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Avi Kivity <avi@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: mmu_notifier: fix inconsistent memory between secondary
 MMU and host

On 08/22/2012 12:12 PM, Hugh Dickins wrote:
> On Wed, 22 Aug 2012, Xiao Guangrong wrote:
>> On 08/21/2012 11:06 PM, Andrea Arcangeli wrote:
>>>
>>> The KSM usage of it looks safe because it will only establish readonly
>>> ptes with it.
>>
>> Hmm, in KSM code, i found this code in replace_page:
>>
>> set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
>>
>> It is possible to establish a writable pte, no?
> 
> No: we only do KSM in private vmas (!VM_SHARED), and because of the
> need to CopyOnWrite in those, vm_page_prot excludes write permission:
> write permission has to be added on COW fault.

After read the code carefully, yes, you are right. Thank you very much
for your explanation, Hugh! :)

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/