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
| ||
|
Date: Tue, 26 May 2020 13:16:14 +0300 From: Liran Alon <liran.alon@...cle.com> To: Mike Rapoport <rppt@...nel.org> Cc: "Kirill A. Shutemov" <kirill@...temov.name>, Dave Hansen <dave.hansen@...ux.intel.com>, Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <sean.j.christopherson@...el.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, Wanpeng Li <wanpengli@...cent.com>, Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>, David Rientjes <rientjes@...gle.com>, Andrea Arcangeli <aarcange@...hat.com>, Kees Cook <keescook@...omium.org>, Will Drewry <wad@...omium.org>, "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>, "Kleen, Andi" <andi.kleen@...el.com>, x86@...nel.org, kvm@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> Subject: Re: [RFC 00/16] KVM protected memory extension On 26/05/2020 9:17, Mike Rapoport wrote: > On Mon, May 25, 2020 at 04:47:18PM +0300, Liran Alon wrote: >> On 22/05/2020 15:51, Kirill A. Shutemov wrote: >> >> Furthermore, I would like to point out that just unmapping guest data from >> kernel direct-map is not sufficient to prevent all >> guest-to-guest info-leaks via a kernel memory info-leak vulnerability. This >> is because host kernel VA space have other regions >> which contains guest sensitive data. For example, KVM per-vCPU struct (which >> holds vCPU state) is allocated on slab and therefore >> still leakable. > Objects allocated from slab use the direct map, vmalloc() is another story. It doesn't matter. This patch series, like XPFO, only removes guest memory pages from direct-map. Not things such as KVM per-vCPU structs. That's why Julian & Marius (AWS), created the "Process local kernel VA region" patch-series that declare a single PGD entry, which maps a kernelspace region, to have different PFN between different tasks. For more information, see my KVM Forum talk slides I gave in previous reply and related AWS patch-series: https://patchwork.kernel.org/cover/10990403/ > >>> - Touching direct mapping leads to fragmentation. We need to be able to >>> recover from it. I have a buggy patch that aims at recovering 2M/1G page. >>> It has to be fixed and tested properly >> As I've mentioned above, not mapping all guest memory from 1GB hugetlbfs >> will lead to holes in kernel direct-map which force it to not be mapped >> anymore as a series of 1GB huge-pages. >> This have non-trivial performance cost. Thus, I am not sure addressing this >> use-case is valuable. > Out of curiosity, do we actually have some numbers for the "non-trivial > performance cost"? For instance for KVM usecase? > Dig into XPFO mailing-list discussions to find out... I just remember that this was one of the main concerns regarding XPFO. -Liran
Powered by blists - more mailing lists