Date: Wed, 29 Mar 2017 13:45:32 -0700 From: "H. Peter Anvin" <hpa@...or.com> To: Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org Cc: Rik van Riel <riel@...hat.com>, Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, x86@...nel.org, Paolo Bonzini <pbonzini@...hat.com>, Radim Krčmář <rkrcmar@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Dave Hansen <dave.hansen@...ux.intel.com>, Yu-cheng Yu <yu-cheng.yu@...el.com>, Masahiro Yamada <yamada.masahiro@...ionext.com>, Borislav Petkov <bp@...e.de>, Christian Borntraeger <borntraeger@...ibm.com>, Thomas Garnier <thgarnie@...gle.com>, Brian Gerst <brgerst@...il.com>, He Chen <he.chen@...ux.intel.com>, Mathias Krause <minipli@...glemail.com>, Fenghua Yu <fenghua.yu@...el.com>, Piotr Luc <piotr.luc@...el.com>, Kyle Huey <me@...ehuey.com>, Len Brown <len.brown@...el.com>, kvm@...r.kernel.org, kernel-hardening@...ts.openwall.com Subject: Re: [PATCH] x86/fpu: move FPU state into separate cache On 03/29/17 13:39, Kees Cook wrote: > This removes ARCH_WANTS_DYNAMIC_TASK_STRUCT from x86, leaving only s390 > still defining this config. > > In order to support future structure layout randomization of the > task_struct, none of the structure fields are allowed to have a specific > position or dynamic size. To enable randomization of task_struct on > x86, the FPU state must be moved to its own dynamically sized cache, > and dereferenced from the task_struct. > > This change is nearly identical to what was done in grsecurity to support > structure layout randomization. Hopefully I found all the needed changes. > This passes allyesconfig, and boot tests. Is this really what we want to happen? It seems much more sane to simply make them adjacent; they don't need to be part of the same structure (in practice, there are three objects: thread_info, task_struct, and the FPU state.) -hpa
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