Date: Tue, 13 Nov 2018 10:36:45 -0800 From: Andy Lutomirski <luto@...nel.org> To: Igor Stoppa <igor.stoppa@...wei.com> Cc: Nadav Amit <nadav.amit@...il.com>, Igor Stoppa <igor.stoppa@...il.com>, Kees Cook <keescook@...omium.org>, Peter Zijlstra <peterz@...radead.org>, Mimi Zohar <zohar@...ux.vnet.ibm.com>, Matthew Wilcox <willy@...radead.org>, Dave Chinner <david@...morbit.com>, James Morris <jmorris@...ei.org>, Michal Hocko <mhocko@...nel.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, linux-integrity <linux-integrity@...r.kernel.org>, LSM List <linux-security-module@...r.kernel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, Jonathan Corbet <corbet@....net>, Laura Abbott <labbott@...hat.com>, Randy Dunlap <rdunlap@...radead.org>, Mike Rapoport <rppt@...ux.vnet.ibm.com>, "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de> Subject: Re: [PATCH 10/17] prmem: documentation On Tue, Nov 13, 2018 at 10:33 AM Igor Stoppa <igor.stoppa@...wei.com> wrote: > > I forgot one sentence :-( > > On 13/11/2018 20:31, Igor Stoppa wrote: > > On 13/11/2018 19:47, Andy Lutomirski wrote: > > > >> For general rare-writish stuff, I don't think we want IRQs running > >> with them mapped anywhere for write. For AVC and IMA, I'm less sure. > > > > Why would these be less sensitive? > > > > But I see a big difference between my initial implementation and this one. > > > > In my case, by using a shared mapping, visible to all cores, freezing > > the core that is performing the write would have exposed the writable > > mapping to a potential attack run from another core. > > > > If the mapping is private to the core performing the write, even if it > > is frozen, it's much harder to figure out what it had mapped and where, > > from another core. > > > > To access that mapping, the attack should be performed from the ISR, I > > think. > > Unless the secondary mapping is also available to other cores, through > the shared mm_struct ? > I don't think this matters much. The other cores will only be able to use that mapping when they're doing a rare write.
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