Date: Tue, 20 Feb 2018 19:16:38 +0200 From: Igor Stoppa <igor.stoppa@...wei.com> To: Laura Abbott <labbott@...hat.com>, Kees Cook <keescook@...omium.org> CC: Boris Lukashev <blukashev@...pervictus.com>, Christopher Lameter <cl@...ux.com>, Matthew Wilcox <willy@...radead.org>, Jann Horn <jannh@...gle.com>, Jerome Glisse <jglisse@...hat.com>, Michal Hocko <mhocko@...nel.org>, Christoph Hellwig <hch@...radead.org>, linux-security-module <linux-security-module@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>, kernel list <linux-kernel@...r.kernel.org>, "Kernel Hardening" <kernel-hardening@...ts.openwall.com> Subject: Re: [PATCH 4/6] Protectable Memory On 13/02/18 20:10, Laura Abbott wrote: > On 02/13/2018 07:20 AM, Igor Stoppa wrote: >> Why alterations of page properties are not considered a risk and the physmap is? >> And how would it be easier (i suppose) to attack the latter? > > Alterations are certainly a risk but with the physmap the > mapping is already there. Find the address and you have > access vs. needing to actually modify the properties > then do the access. I could also be complete off base > on my threat model here so please correct me if I'm > wrong. It's difficult for me to comment on this without knowing *how* the attack would be performed, in your model. Ex: my expectation is that the attacked has R/W access to kernel data and has knowledge of the location of static variables. This is not just a guess, but a real-life scenario, found in attacks that, among other things, are capable of disabling SELinux, to proceed toward gaining full root capability. At that point, I think that variables which are allocated dynamically, in vmalloc address space, are harder to locate, because of the virtual mapping and the randomness of the address chosen (this I have not confirmed yet, but I suppose there is some randomness in picking the address to assign to a certain allocation request to vmalloc, otherwise, it could be added). > I think your other summaries are good points though > and should go in the cover letter. Ok, I'm just afraid it risks becoming a lengthy dissertation :-) -- igor
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