Date: Thu, 19 Jan 2017 14:00:57 -0800 From: Kees Cook <keescook@...omium.org> To: Mark Rutland <mark.rutland@....com>, Michael Ellerman <mpe@...erman.id.au> Cc: Laura Abbott <labbott@...hat.com>, Jason Wessel <jason.wessel@...driver.com>, Jonathan Corbet <corbet@....net>, Russell King <linux@...linux.org.uk>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, "James E.J. Bottomley" <jejb@...isc-linux.org>, Helge Deller <deller@....de>, Martin Schwidefsky <schwidefsky@...ibm.com>, Heiko Carstens <heiko.carstens@...ibm.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>, Rob Herring <robh@...nel.org>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>, Jessica Yu <jeyu@...hat.com>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, linux-parisc <linux-parisc@...r.kernel.org>, "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>, Linux PM list <linux-pm@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com> Subject: Re: [PATCH 1/2] security: Change name of CONFIG_DEBUG_RODATA On Thu, Jan 19, 2017 at 2:56 AM, Mark Rutland <mark.rutland@....com> wrote: > Hi Laura, > > On Wed, Jan 18, 2017 at 05:29:05PM -0800, Laura Abbott wrote: >> diff --git a/security/Kconfig b/security/Kconfig >> index 118f454..ad6ce82 100644 >> --- a/security/Kconfig >> +++ b/security/Kconfig >> @@ -158,6 +158,22 @@ config HARDENED_USERCOPY_PAGESPAN >> been removed. This config is intended to be used only while >> trying to find such users. >> >> +config ARCH_HAS_HARDENED_MAPPINGS >> + def_bool n >> + >> +config HARDENED_PAGE_MAPPINGS >> + bool "Mark kernel mappings with stricter permissions (RO/W^X)" >> + default y >> + depends on ARCH_HAS_HARDENED_MAPPINGS >> + help >> + If this is set, kernel text and rodata memory will be made read-only, >> + and non-text memory will be made non-executable. This provides >> + protection against certain security attacks (e.g. executing the heap >> + or modifying text). >> + >> + Unless your system has known restrictions or performance issues, it >> + is recommended to say Y here. > > It's somewhat unfortunate that this means the feature is no longer > mandatory on arm64 (and s390+x86). We have a boot-time switch to turn > the protections off, so I was hoping we could make this mandatory on all > architectures with support. Oh, I totally missed this. Yes, we need it to stay mandatory. It should be possible by just adding "select HARDENED_PAGE_MAPPINGS" to the arch Kconfig, yes? > It would be good to see if we could make this mandatory for arm and > parisc, or if it really needs to be optional for either of those. (Adding mpe to CC...) Michael, what's needed to get this working on powerpc too? -Kees -- Kees Cook Nexus Security
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