Date: Mon, 10 Apr 2017 11:22:59 +0100 From: Mark Rutland <mark.rutland@....com> To: Andy Lutomirski <luto@...nel.org> Cc: Daniel Micay <danielmicay@...il.com>, Mathias Krause <minipli@...glemail.com>, Thomas Gleixner <tglx@...utronix.de>, Kees Cook <keescook@...omium.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Hoeun Ryu <hoeun.ryu@...il.com>, PaX Team <pageexec@...email.hu>, Emese Revfy <re.emese@...il.com>, Russell King <linux@...linux.org.uk>, X86 ML <x86@...nel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, Peter Zijlstra <peterz@...radead.org> Subject: Re: Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() On Sat, Apr 08, 2017 at 08:20:03AM -0700, Andy Lutomirski wrote: > On Sat, Apr 8, 2017 at 12:33 AM, Daniel Micay <danielmicay@...il.com> wrote: > > The > > submitted code is aimed at rare writes to globals, but this feature is > > more than that and design decisions shouldn't be based on just the > > short term. > > Then, if you disagree with a proposed design, *explain why* in a > standalone manner. Say what future uses a different design would > have. > > > I actually care a lot more about 64-bit ARM support than I do x86, but > > using a portable API for pax_open_kernel (for the simple uses at > > least) is separate from choosing the underlying implementation. There > > might not be a great way to do it on the architectures I care about > > but that doesn't need to hinder x86. It's really not that much code... > > A weaker/slower implementation for x86 also encourages the same > > elsewhere. > > No one has explained how CR0.WP is weaker or slower than my proposal. > Here's what I'm proposing: > > At boot, choose a random address A. Create an mm_struct that has a > single VMA starting at A that represents the kernel's rarely-written > section. Compute O = (A - VA of rarely-written section). To do a > rare write, use_mm() the mm, write to (VA + O), then unuse_mm(). > > This should work on any arch that has an MMU that allows this type of > aliasing and that doesn't have PA-based protections on the > rarely-written section. Modulo randomization, that sounds exactly like what I had envisaged , so that makes sense to me. Thanks, Mark.  http://www.openwall.com/lists/kernel-hardening/2016/11/18/3
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.