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Message-ID: <CAGXu5j+Nj-u3GXDTAoCR0wymMWzOKy3KvRLUybY4ApctCQiL9Q@mail.gmail.com>
Date: Mon, 4 Dec 2017 10:19:26 -0800
From: Kees Cook <keescook@...omium.org>
To: Will Deacon <will.deacon@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, LKML <linux-kernel@...r.kernel.org>,
kernel-hardening@...ts.openwall.com, Mark Rutland <mark.rutland@....com>,
Laura Abbott <labbott@...hat.com>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH] Kconfig: Make STRICT_DEVMEM default-y on x86 and arm64
On Mon, Dec 4, 2017 at 7:56 AM, Will Deacon <will.deacon@....com> wrote:
> On Fri, Dec 01, 2017 at 12:10:00PM -0800, Kees Cook wrote:
>> Distros have been shipping with CONFIG_STRICT_DEVMEM=y for years now. It
>> is probably time to flip this default for x86 and arm64.
>
> Should we be defaulting IO_STRICT_DEVMEM on as well?
I'd love to see that, but I haven't seen a long history on this
setting yet. It may be that arm64 can do it, since it doesn't have the
x86 hardware legacy stuff ... If you're willing to give it a shot, I'm
all for it. :)
-Kees
>
> Will
>
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>> ---
>> lib/Kconfig.debug | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index 947d3e2ed5c2..39b123d04a36 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -1985,7 +1985,7 @@ config STRICT_DEVMEM
>> bool "Filter access to /dev/mem"
>> depends on MMU && DEVMEM
>> depends on ARCH_HAS_DEVMEM_IS_ALLOWED
>> - default y if TILE || PPC
>> + default y if TILE || PPC || X86 || ARM64
>> ---help---
>> If this option is disabled, you allow userspace (root) access to all
>> of memory, including kernel and userspace memory. Accidental
>> --
>> 2.7.4
>>
>>
>> --
>> Kees Cook
>> Pixel Security
--
Kees Cook
Pixel Security
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