linux-kernel - Re: [PATCH 1/2] KVM: MMU: fix ept=0/pte.u=0/pte.w=0/CR0.WP=0/CR4.SMEP=1/EFER.NX=0 combo

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: <56E13454.3080604@linux.intel.com>
Date:	Thu, 10 Mar 2016 16:46:12 +0800
From:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
To:	Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc:	stable@...r.kernel.org, Xiao Guangrong <guangrong.xiao@...hat.com>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH 1/2] KVM: MMU: fix
 ept=0/pte.u=0/pte.w=0/CR0.WP=0/CR4.SMEP=1/EFER.NX=0 combo



On 03/08/2016 07:44 PM, Paolo Bonzini wrote:
> Yes, all of these are needed. :) This is admittedly a bit odd, but
> kvm-unit-tests access.flat tests this if you run it with "-cpu host"
> and of course ept=0.
>
> KVM handles supervisor writes of a pte.u=0/pte.w=0/CR0.WP=0 page by
> setting U=0 and W=1 in the shadow PTE.  This will cause a user write
> to fault and a supervisor write to succeed (which is correct because
> CR0.WP=0).  A user read instead will flip U=0 to 1 and W=1 back to 0.

BTW, it should be pte.u = 1 where you mentioned above.