From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "Shankar, Ravi V" <ravi.v.shankar@intel.com>,
"bsingharora@gmail.com" <bsingharora@gmail.com>,
"hpa@zytor.com" <hpa@zytor.com>,
"Syromiatnikov, Eugene" <esyr@redhat.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"rdunlap@infradead.org" <rdunlap@infradead.org>,
"keescook@chromium.org" <keescook@chromium.org>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"kirill.shutemov@linux.intel.com"
<kirill.shutemov@linux.intel.com>,
"Eranian, Stephane" <eranian@google.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"fweimer@redhat.com" <fweimer@redhat.com>,
"nadav.amit@gmail.com" <nadav.amit@gmail.com>,
"jannh@google.com" <jannh@google.com>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"kcc@google.com" <kcc@google.com>, "bp@alien8.de" <bp@alien8.de>,
"oleg@redhat.com" <oleg@redhat.com>,
"hjl.tools@gmail.com" <hjl.tools@gmail.com>,
"Yang, Weijiang" <weijiang.yang@intel.com>,
"Lutomirski, Andy" <luto@kernel.org>,
"pavel@ucw.cz" <pavel@ucw.cz>, "arnd@arndb.de" <arnd@arndb.de>,
"Moreira, Joao" <joao.moreira@intel.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mike.kravetz@oracle.com" <mike.kravetz@oracle.com>,
"x86@kernel.org" <x86@kernel.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"Dave.Martin@arm.com" <Dave.Martin@arm.com>,
"john.allen@amd.com" <john.allen@amd.com>,
"mingo@redhat.com" <mingo@redhat.com>,
"Hansen, Dave" <dave.hansen@intel.com>,
"corbet@lwn.net" <corbet@lwn.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
"gorcunov@gmail.com" <gorcunov@gmail.com>
Cc: "hch@lst.de" <hch@lst.de>, "Yu, Yu-cheng" <yu-cheng.yu@intel.com>
Subject: Re: [PATCH 07/35] x86/mm: Remove _PAGE_DIRTY from kernel RO pages
Date: Tue, 8 Feb 2022 22:52:29 +0000 [thread overview]
Message-ID: <bdb2711ae5ff0fc204ffcfd8ddccf3c2e105f297.camel@intel.com> (raw)
In-Reply-To: <672fa390-c88c-4e2a-aa42-52d171acfd62@intel.com>
On Mon, 2022-02-07 at 16:13 -0800, Dave Hansen wrote:
> On 1/30/22 13:18, Rick Edgecombe wrote:
> > The x86 family of processors do not directly create read-only and
> > Dirty
> > PTEs. These PTEs are created by software.
>
> That's not strictly correct.
>
> There's nothing in the architecture today to prevent the CPU from
> creating Write=0,Dirty=1 PTEs. In fact, some CPUs do this in weird
> situations. It wouldn't be wrong to say:
>
> Processors sometimes directly create read-only and Dirty PTEs.
>
> which is the opposite of what is written above. This is why the CET
> spec has the blurb about shadow-stack-supporting CPUs promise not to
> do
> this any more.
Yea, it's wrong. The whole point of the new assurance is that it could
before as you say.
>
> > One such case is that kernel
> > read-only pages are historically setup as Dirty.
>
> ^ set up
>
> > New processors that support Shadow Stack regard read-only and Dirty
> > PTEs as
> > shadow stack pages.
>
> This also isn't *quite* correct. It's not just having a new
> processor,
> it includes enabling shadow stacks.
Right.
>
> > This results in ambiguity between shadow stack and kernel read-only
> > pages. To resolve this, removed Dirty from kernel read- only
> > pages.
>
> One thing that's not clear from the spec: does this cause an *actual*
> problem? For instance, does setting:
>
> IA32_U_CET.SH_STK_EN=1
> but
> IA32_S_CET.SH_STK_EN=0
>
> means that shadow stacks are enforced in user *MODE* or on
> user-paging-permission (U=0) PTEs?
>
> I think it's modes, but it would be nice to be clear. *BUT*, if this
> is
> accurate, doesn't it also mean that this patch is not strictly
> necessary?
>
> Don't get me wrong, the patch is probably still a good idea, but
> let's
> make sure we get the exact reasoning clear.
Yea, I think this is just a tying up loose ends thing. It is not
functionally needed until there would be shadow stack mode for kernel.
I'll update the patch to make this clear.
next prev parent reply other threads:[~2022-02-08 22:53 UTC|newest]
Thread overview: 152+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-30 21:18 [PATCH 00/35] Shadow stacks for userspace Rick Edgecombe
2022-01-30 21:18 ` [PATCH 01/35] Documentation/x86: Add CET description Rick Edgecombe
2022-01-30 21:18 ` [PATCH 02/35] x86/cet/shstk: Add Kconfig option for Shadow Stack Rick Edgecombe
2022-02-07 22:39 ` Dave Hansen
2022-02-08 8:41 ` Thomas Gleixner
2022-02-08 20:20 ` Edgecombe, Rick P
2022-02-08 8:39 ` Thomas Gleixner
2022-01-30 21:18 ` [PATCH 03/35] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Rick Edgecombe
2022-02-07 22:45 ` Dave Hansen
2022-02-08 20:23 ` Edgecombe, Rick P
2022-02-09 1:10 ` Kees Cook
2022-01-30 21:18 ` [PATCH 04/35] x86/cpufeatures: Introduce CPU setup and option parsing for CET Rick Edgecombe
2022-02-07 22:49 ` Dave Hansen
2022-02-08 20:29 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 05/35] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Rick Edgecombe
2022-02-07 23:28 ` Dave Hansen
2022-02-08 21:36 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 06/35] x86/cet: Add control-protection fault handler Rick Edgecombe
2022-02-07 23:56 ` Dave Hansen
2022-02-08 22:23 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 07/35] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Rick Edgecombe
2022-02-08 0:13 ` Dave Hansen
2022-02-08 22:52 ` Edgecombe, Rick P [this message]
2022-01-30 21:18 ` [PATCH 08/35] x86/mm: Move pmd_write(), pud_write() up in the file Rick Edgecombe
2022-01-30 21:18 ` [PATCH 09/35] x86/mm: Introduce _PAGE_COW Rick Edgecombe
2022-02-08 1:05 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 10/35] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Rick Edgecombe
2022-02-09 16:58 ` Dave Hansen
2022-02-11 1:39 ` Edgecombe, Rick P
2022-02-11 7:13 ` Wang, Zhi A
2022-02-12 1:45 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 11/35] x86/mm: Update pte_modify for _PAGE_COW Rick Edgecombe
2022-02-09 18:00 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 12/35] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Rick Edgecombe
2022-02-09 18:30 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 13/35] mm: Move VM_UFFD_MINOR_BIT from 37 to 38 Rick Edgecombe
2022-01-30 21:18 ` [PATCH 14/35] mm: Introduce VM_SHADOW_STACK for shadow stack memory Rick Edgecombe
2022-02-09 21:55 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 15/35] x86/mm: Check Shadow Stack page fault errors Rick Edgecombe
2022-02-09 19:06 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 16/35] x86/mm: Update maybe_mkwrite() for shadow stack Rick Edgecombe
2022-02-09 21:16 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 17/35] mm: Fixup places that call pte_mkwrite() directly Rick Edgecombe
2022-02-09 21:51 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 18/35] mm: Add guard pages around a shadow stack Rick Edgecombe
2022-02-09 22:23 ` Dave Hansen
2022-02-10 22:38 ` David Laight
2022-02-10 23:42 ` Edgecombe, Rick P
2022-02-11 9:08 ` David Laight
2022-02-10 22:43 ` Dave Hansen
2022-02-10 23:07 ` Andy Lutomirski
2022-02-10 23:40 ` Edgecombe, Rick P
2022-02-11 17:54 ` Andy Lutomirski
2022-02-12 0:10 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 19/35] mm/mmap: Add shadow stack pages to memory accounting Rick Edgecombe
2022-02-09 22:27 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 20/35] mm: Update can_follow_write_pte() for shadow stack Rick Edgecombe
2022-02-09 22:50 ` Dave Hansen
2022-02-09 22:52 ` Dave Hansen
2022-02-10 22:45 ` David Laight
2022-01-30 21:18 ` [PATCH 21/35] mm/mprotect: Exclude shadow stack from preserve_write Rick Edgecombe
2022-02-10 19:27 ` Dave Hansen
2022-01-30 21:18 ` [PATCH 22/35] x86/mm: Prevent VM_WRITE shadow stacks Rick Edgecombe
2022-02-11 22:19 ` Dave Hansen
2022-02-12 1:44 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 23/35] x86/fpu: Add helpers for modifying supervisor xstate Rick Edgecombe
2022-02-08 8:51 ` Thomas Gleixner
2022-02-09 19:55 ` Edgecombe, Rick P
2022-02-12 0:27 ` Dave Hansen
2022-02-12 2:31 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 24/35] mm: Re-introduce vm_flags to do_mmap() Rick Edgecombe
2022-01-30 21:18 ` [PATCH 25/35] x86/cet/shstk: Add user-mode shadow stack support Rick Edgecombe
2022-02-11 23:37 ` Dave Hansen
2022-02-12 0:07 ` Andy Lutomirski
2022-02-12 0:11 ` Dave Hansen
2022-02-12 0:12 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 26/35] x86/process: Change copy_thread() argument 'arg' to 'stack_size' Rick Edgecombe
2022-02-08 8:38 ` Thomas Gleixner
2022-02-11 2:09 ` Edgecombe, Rick P
2022-02-14 12:33 ` Jann Horn
2022-02-15 1:22 ` Edgecombe, Rick P
2022-02-15 8:49 ` Christian Brauner
2022-01-30 21:18 ` [PATCH 27/35] x86/fpu: Add unsafe xsave buffer helpers Rick Edgecombe
2022-01-30 21:18 ` [PATCH 28/35] x86/cet/shstk: Handle thread shadow stack Rick Edgecombe
2022-01-30 21:18 ` [PATCH 29/35] x86/cet/shstk: Introduce shadow stack token setup/verify routines Rick Edgecombe
2022-01-30 21:18 ` [PATCH 30/35] x86/cet/shstk: Handle signals for shadow stack Rick Edgecombe
2022-01-30 21:18 ` [PATCH 31/35] x86/cet/shstk: Add arch_prctl elf feature functions Rick Edgecombe
2022-01-30 21:18 ` [PATCH 32/35] x86/cet/shstk: Introduce map_shadow_stack syscall Rick Edgecombe
2022-01-30 21:18 ` [PATCH 33/35] selftests/x86: Add map_shadow_stack syscall test Rick Edgecombe
2022-02-03 22:42 ` Dave Hansen
2022-02-04 1:22 ` Edgecombe, Rick P
2022-01-30 21:18 ` [PATCH 34/35] x86/cet/shstk: Support wrss for userspace Rick Edgecombe
2022-01-31 7:56 ` Florian Weimer
2022-01-31 18:26 ` H.J. Lu
2022-01-31 18:45 ` Florian Weimer
2022-01-30 21:18 ` [PATCH 35/35] x86/cpufeatures: Limit shadow stack to Intel CPUs Rick Edgecombe
2022-02-03 21:58 ` John Allen
2022-02-03 22:23 ` H.J. Lu
2022-02-04 22:21 ` John Allen
2022-02-03 21:07 ` [PATCH 00/35] Shadow stacks for userspace Thomas Gleixner
2022-02-04 1:08 ` Edgecombe, Rick P
2022-02-04 5:20 ` Andy Lutomirski
2022-02-04 20:23 ` Edgecombe, Rick P
2022-02-05 13:26 ` David Laight
2022-02-05 13:29 ` H.J. Lu
2022-02-05 20:15 ` Edgecombe, Rick P
2022-02-05 20:21 ` H.J. Lu
2022-02-06 13:19 ` Peter Zijlstra
2022-02-06 13:42 ` David Laight
2022-02-06 13:55 ` H.J. Lu
2022-02-07 10:22 ` Florian Weimer
2022-02-08 1:46 ` Edgecombe, Rick P
2022-02-08 1:31 ` Andy Lutomirski
2022-02-08 9:31 ` Thomas Gleixner
2022-02-08 16:15 ` Andy Lutomirski
2022-02-06 13:06 ` Peter Zijlstra
2022-02-06 18:42 ` Mike Rapoport
2022-02-07 7:20 ` Adrian Reber
2022-02-07 16:30 ` Dave Hansen
2022-02-08 9:16 ` Mike Rapoport
2022-02-08 9:29 ` Cyrill Gorcunov
2022-02-08 16:21 ` Andy Lutomirski
2022-02-08 17:02 ` Cyrill Gorcunov
2022-02-09 2:18 ` Edgecombe, Rick P
2022-02-09 6:43 ` Cyrill Gorcunov
2022-02-09 10:53 ` Mike Rapoport
2022-02-10 2:37 ` Andy Lutomirski
2022-02-10 2:53 ` H.J. Lu
2022-02-10 13:52 ` Willgerodt, Felix
2022-02-11 7:41 ` avagin
2022-02-11 8:04 ` Mike Rapoport
2022-02-28 20:27 ` Mike Rapoport
2022-02-28 20:30 ` Andy Lutomirski
2022-02-28 21:30 ` Mike Rapoport
2022-02-28 22:55 ` Andy Lutomirski
2022-03-03 19:40 ` Mike Rapoport
2022-03-03 23:00 ` Andy Lutomirski
2022-03-04 1:30 ` Edgecombe, Rick P
2022-03-04 19:13 ` Andy Lutomirski
2022-03-07 18:56 ` Mike Rapoport
2022-03-07 19:07 ` H.J. Lu
2022-05-31 11:59 ` Mike Rapoport
2022-05-31 16:25 ` Edgecombe, Rick P
2022-05-31 16:36 ` Mike Rapoport
2022-05-31 17:34 ` Edgecombe, Rick P
2022-05-31 18:00 ` H.J. Lu
2022-06-01 17:27 ` Edgecombe, Rick P
2022-06-01 19:27 ` H.J. Lu
2022-06-01 8:06 ` Mike Rapoport
2022-06-01 17:24 ` Edgecombe, Rick P
2022-06-09 18:04 ` Mike Rapoport
2022-03-07 22:21 ` David Laight
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=bdb2711ae5ff0fc204ffcfd8ddccf3c2e105f297.camel@intel.com \
--to=rick.p.edgecombe@intel.com \
--cc=Dave.Martin@arm.com \
--cc=arnd@arndb.de \
--cc=bp@alien8.de \
--cc=bsingharora@gmail.com \
--cc=corbet@lwn.net \
--cc=dave.hansen@intel.com \
--cc=dave.hansen@linux.intel.com \
--cc=eranian@google.com \
--cc=esyr@redhat.com \
--cc=fweimer@redhat.com \
--cc=gorcunov@gmail.com \
--cc=hch@lst.de \
--cc=hjl.tools@gmail.com \
--cc=hpa@zytor.com \
--cc=jannh@google.com \
--cc=joao.moreira@intel.com \
--cc=john.allen@amd.com \
--cc=kcc@google.com \
--cc=keescook@chromium.org \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=mike.kravetz@oracle.com \
--cc=mingo@redhat.com \
--cc=nadav.amit@gmail.com \
--cc=oleg@redhat.com \
--cc=pavel@ucw.cz \
--cc=peterz@infradead.org \
--cc=ravi.v.shankar@intel.com \
--cc=rdunlap@infradead.org \
--cc=tglx@linutronix.de \
--cc=weijiang.yang@intel.com \
--cc=x86@kernel.org \
--cc=yu-cheng.yu@intel.com \
/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;
as well as URLs for NNTP newsgroup(s).