From: Dave Hansen <dave.hansen@linux.intel.com>
To: Nadav Amit <namit@vmware.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Andy Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
"keescook@google.com" <keescook@google.com>,
"hughd@google.com" <hughd@google.com>,
"jgross@suse.com" <jgross@suse.com>,
"x86@kernel.org" <x86@kernel.org>
Subject: Re: [RFC][PATCH 03/10] x86/mm: introduce "default" kernel PTE mask
Date: Thu, 22 Feb 2018 14:26:43 -0800 [thread overview]
Message-ID: <61c68587-3ad5-edf7-539c-8af99c6220ea@linux.intel.com> (raw)
In-Reply-To: <57A9625E-3F25-402B-8B54-129A68449C48@vmware.com>
On 02/22/2018 02:21 PM, Nadav Amit wrote:
> Dave Hansen <dave.hansen@linux.intel.com> wrote:
>> From: Dave Hansen <dave.hansen@linux.intel.com>
>> The __PAGE_KERNEL_* page permissions are "raw". They contain bits
>> that may or may not be supported on the current processor. They
>> need to be filtered by a mask (currently __supported_pte_mask) to
>> turn them into a value that we can actually set in a PTE.
>>
>> These __PAGE_KERNEL_* values all contain _PAGE_GLOBAL. But, with
>> PTI, we want to be able to support _PAGE_GLOBAL (have the bit set
>> in __supported_pte_mask) but not have it appear in any of these
>> masks by default.
>
> There might be a potential issue with this approach. __supported_pte_mask is
> exported, so out-of-tree modules might use it. They therefore can
> unknowingly use this value to set PTEs with _PAGE_GLOBAL set.
I don't think we can help out-of-tree modules getting this wrong.
They're OK if they use PAGE_KERNEL*, btw.
next prev parent reply other threads:[~2018-02-22 22:26 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-22 20:36 [RFC][PATCH 00/10] Use global pages with PTI Dave Hansen
2018-02-22 20:36 ` [RFC][PATCH 01/10] x86/mm: factor out pageattr _PAGE_GLOBAL setting Dave Hansen
2018-02-22 20:36 ` [RFC][PATCH 02/10] x86/mm: undo double _PAGE_PSE clearing Dave Hansen
2018-02-22 20:36 ` [RFC][PATCH 03/10] x86/mm: introduce "default" kernel PTE mask Dave Hansen
2018-02-22 22:21 ` Nadav Amit
2018-02-22 22:26 ` Dave Hansen [this message]
2018-02-22 23:11 ` Tom Lendacky
2018-02-23 23:46 ` Dave Hansen
2018-02-22 20:36 ` [RFC][PATCH 04/10] x86/espfix: use kernel-default " Dave Hansen
2018-02-22 21:27 ` Nadav Amit
2018-02-22 21:30 ` Dave Hansen
2018-02-22 21:59 ` Andy Lutomirski
2018-02-22 22:05 ` Dave Hansen
2018-02-22 20:37 ` [RFC][PATCH 05/10] x86/mm: do not auto-massage page protections Dave Hansen
2018-02-22 21:46 ` Nadav Amit
2018-02-22 21:52 ` Dave Hansen
2018-02-22 20:37 ` [RFC][PATCH 06/10] x86/mm: remove extra filtering in pageattr code Dave Hansen
2018-02-22 20:37 ` [RFC][PATCH 07/10] x86/mm: comment _PAGE_GLOBAL mystery Dave Hansen
2018-02-22 20:37 ` [RFC][PATCH 08/10] x86/mm: do not forbid _PAGE_RW before init for __ro_after_init Dave Hansen
2018-02-22 20:53 ` Kees Cook
2018-02-22 20:37 ` [RFC][PATCH 09/10] x86/pti: enable global pages for shared areas Dave Hansen
2018-02-22 20:37 ` [RFC][PATCH 10/10] x86/pti: clear _PAGE_GLOBAL for kernel image Dave Hansen
2018-02-22 21:52 ` [RFC][PATCH 00/10] Use global pages with PTI Linus Torvalds
2018-02-24 1:49 ` Dave Hansen
2018-02-24 4:20 ` Linus Torvalds
2018-02-24 4:34 ` [RFC][PATCH 00/10] Use global pages with PTI - Truth about the white man thetruthbeforeus
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