From: Dave Hansen <dave.hansen@linux.intel.com>
To: Nadav Amit <namit@vmware.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"aarcange@redhat.com" <aarcange@redhat.com>,
"luto@kernel.org" <luto@kernel.org>,
"torvalds@linux-foundation.org" <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 04/10] x86/espfix: use kernel-default PTE mask
Date: Thu, 22 Feb 2018 13:30:01 -0800 [thread overview]
Message-ID: <f90cef60-1710-1d99-61ee-4527067b115f@linux.intel.com> (raw)
In-Reply-To: <93613F56-C778-4EA0-8945-A0B8ABC1A5FD@vmware.com>
On 02/22/2018 01:27 PM, Nadav Amit wrote:
> Dave Hansen <dave.hansen@linux.intel.com> wrote:
>> From: Dave Hansen <dave.hansen@linux.intel.com>
>> In creating its page tables, the espfix code masks its PGTABLE_PROT
>> value with the supported mask: __supported_pte_mask. This ensures
>> that unsupported bits are not set in the final PTE. But, it also
>> sets _PAGE_GLOBAL which we do not want for PTE. Use
>> __default_kernel_pte_mask instead which clears _PAGE_GLOBAL for PTI.
>
> Can you please explain what is your concern? Exposing more gadgets for
> speculative ROP attacks?
>
> Or is it a general rule of not exposing any kernel code &data more than
> absolutely necessary?
I think it's good practice to just expose only the *minimal* amount of
data necessary. It's easier to audit and less likely to expose things
accidentall.
next prev parent reply other threads:[~2018-02-22 21:30 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
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=f90cef60-1710-1d99-61ee-4527067b115f@linux.intel.com \
--to=dave.hansen@linux.intel.com \
--cc=aarcange@redhat.com \
--cc=hughd@google.com \
--cc=jgross@suse.com \
--cc=keescook@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=namit@vmware.com \
--cc=torvalds@linux-foundation.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox