From: Peter Zijlstra <peterz@infradead.org>
To: Kees Cook <keescook@chromium.org>
Cc: Igor Stoppa <igor.stoppa@gmail.com>,
Mimi Zohar <zohar@linux.vnet.ibm.com>,
Matthew Wilcox <willy@infradead.org>,
Dave Chinner <david@fromorbit.com>,
James Morris <jmorris@namei.org>,
Michal Hocko <mhocko@kernel.org>,
Kernel Hardening <kernel-hardening@lists.openwall.com>,
linux-integrity <linux-integrity@vger.kernel.org>,
linux-security-module <linux-security-module@vger.kernel.org>,
Igor Stoppa <igor.stoppa@huawei.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Jonathan Corbet <corbet@lwn.net>,
Laura Abbott <labbott@redhat.com>,
Randy Dunlap <rdunlap@infradead.org>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 10/17] prmem: documentation
Date: Sun, 28 Oct 2018 19:31:26 +0100 [thread overview]
Message-ID: <20181028183126.GB744@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAGXu5jKCs01jvtvpEFS7R8qCR-5iRqK11kJxLJY99NicGWc4aQ@mail.gmail.com>
On Fri, Oct 26, 2018 at 11:46:28AM +0100, Kees Cook wrote:
> On Fri, Oct 26, 2018 at 10:26 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > I still don't really understand the whole write-rare thing; how does it
> > really help? If we can write in kernel memory, we can write to
> > page-tables too.
> One aspect of hardening the kernel against attack is reducing the
> internal attack surface. Not all flaws are created equal, so there is
> variation in what limitations an attacker may have when exploiting
> flaws (not many flaws end up being a fully controlled "write anything,
> anywhere, at any time"). By making the more sensitive data structures
> of the kernel read-only, we reduce the risk of an attacker finding a
> path to manipulating the kernel's behavior in a significant way.
>
> Examples of typical sensitive targets are function pointers, security
> policy, and page tables. Having these "read only at rest" makes them
> much harder to control by an attacker using memory integrity flaws.
Because 'write-anywhere' exploits are easier than (and the typical first
step to) arbitrary code execution thingies?
> The "write rarely" name itself may not sufficiently describe what is
> wanted either (I'll take the blame for the inaccurate name), so I'm
> open to new ideas there. The implementation requirements for the
> "sensitive data read-only at rest" feature are rather tricky:
>
> - allow writes only from specific places in the kernel
> - keep those locations inline to avoid making them trivial ROP targets
> - keep the writeability window open only to a single uninterruptable CPU
The current patch set does not achieve that because it uses a global
address space for the alias mapping (vmap) which is equally accessible
from all CPUs.
> - fast enough to deal with page table updates
The proposed implementation needs page-tables for the alias; I don't see
how you could ever do R/O page-tables when you need page-tables to
modify your page-tables.
And this is entirely irrespective of performance.
> The proposal I made a while back only covered .data things (and used
> x86-specific features).
Oh, right, that CR0.WP stuff.
> Igor's proposal builds on this by including a
> way to do this with dynamic allocation too, which greatly expands the
> scope of structures that can be protected. Given that the x86-only
> method of write-window creation was firmly rejected, this is a new
> proposal for how to do it (vmap window). Using switch_mm() has also
> been suggested, etc.
Right... /me goes find the patches we did for text_poke. Hmm, those
never seem to have made it:
https://lkml.kernel.org/r/20180902173224.30606-1-namit@vmware.com
like that. That approach will in fact work and not be a completely
broken mess like this thing.
> We need to find a good way to do the write-windowing that works well
> for static and dynamic structures _and_ for the page tables... this
> continues to be tricky.
>
> Making it resilient against ROP-style targets makes it difficult to
> deal with certain data structures (like list manipulation). In my
> earlier RFC, I tried to provide enough examples of where this could
> get used to let people see some of the complexity[1]. Igor's series
> expands this to even more examples using dynamic allocation.
Doing 2 CR3 writes for 'every' WR write doesn't seem like it would be
fast enough for much of anything.
And I don't suppose we can take the WP fault and then fix up from there,
because if we're doing R/O page-tables, that'll incrase the fault depth
and we'll double fault all the time, and tripple fault where we
currently double fault. And we all know how _awesome_ tripple faults
are.
But duplicating (and wrapping in gunk) whole APIs is just not going to
work.
next prev parent reply other threads:[~2018-10-28 18:32 UTC|newest]
Thread overview: 140+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-23 21:34 [RFC v1 PATCH 00/17] prmem: protected memory Igor Stoppa
2018-10-23 21:34 ` [PATCH 01/17] prmem: linker section for static write rare Igor Stoppa
2018-10-23 21:34 ` [PATCH 02/17] prmem: write rare for static allocation Igor Stoppa
2018-10-25 0:24 ` Dave Hansen
2018-10-29 18:03 ` Igor Stoppa
2018-10-26 9:41 ` Peter Zijlstra
2018-10-29 20:01 ` Igor Stoppa
2018-10-23 21:34 ` [PATCH 03/17] prmem: vmalloc support for dynamic allocation Igor Stoppa
2018-10-25 0:26 ` Dave Hansen
2018-10-29 18:07 ` Igor Stoppa
2018-10-23 21:34 ` [PATCH 04/17] prmem: " Igor Stoppa
2018-10-23 21:34 ` [PATCH 05/17] prmem: shorthands for write rare on common types Igor Stoppa
2018-10-25 0:28 ` Dave Hansen
2018-10-29 18:12 ` Igor Stoppa
2018-10-23 21:34 ` [PATCH 06/17] prmem: test cases for memory protection Igor Stoppa
2018-10-24 3:27 ` Randy Dunlap
2018-10-24 14:24 ` Igor Stoppa
2018-10-25 16:43 ` Dave Hansen
2018-10-29 18:16 ` Igor Stoppa
2018-10-23 21:34 ` [PATCH 07/17] prmem: lkdtm tests " Igor Stoppa
2018-10-23 21:34 ` [PATCH 08/17] prmem: struct page: track vmap_area Igor Stoppa
2018-10-24 3:12 ` Matthew Wilcox
2018-10-24 23:01 ` Igor Stoppa
2018-10-25 2:13 ` Matthew Wilcox
2018-10-29 18:21 ` Igor Stoppa
2018-10-23 21:34 ` [PATCH 09/17] prmem: hardened usercopy Igor Stoppa
2018-10-29 11:45 ` Chris von Recklinghausen
2018-10-29 18:24 ` Igor Stoppa
2018-10-23 21:34 ` [PATCH 10/17] prmem: documentation Igor Stoppa
2018-10-24 3:48 ` Randy Dunlap
2018-10-24 14:30 ` Igor Stoppa
2018-10-24 23:04 ` Mike Rapoport
2018-10-29 19:05 ` Igor Stoppa
2018-10-26 9:26 ` Peter Zijlstra
2018-10-26 10:20 ` Matthew Wilcox
2018-10-29 19:28 ` Igor Stoppa
2018-10-26 10:46 ` Kees Cook
2018-10-28 18:31 ` Peter Zijlstra [this message]
2018-10-29 21:04 ` Igor Stoppa
2018-10-30 15:26 ` Peter Zijlstra
2018-10-30 16:37 ` Kees Cook
2018-10-30 17:06 ` Andy Lutomirski
2018-10-30 17:58 ` Matthew Wilcox
2018-10-30 18:03 ` Dave Hansen
2018-10-31 9:18 ` Peter Zijlstra
2018-10-30 18:28 ` Tycho Andersen
2018-10-30 19:20 ` Matthew Wilcox
2018-10-30 20:43 ` Igor Stoppa
2018-10-30 21:02 ` Andy Lutomirski
2018-10-30 21:07 ` Kees Cook
2018-10-30 21:25 ` Igor Stoppa
2018-10-30 22:15 ` Igor Stoppa
2018-10-31 10:11 ` Peter Zijlstra
2018-10-31 20:38 ` Andy Lutomirski
2018-10-31 20:53 ` Andy Lutomirski
2018-10-31 9:45 ` Peter Zijlstra
2018-10-30 21:35 ` Matthew Wilcox
2018-10-30 21:49 ` Igor Stoppa
2018-10-31 4:41 ` Andy Lutomirski
2018-10-31 9:08 ` Igor Stoppa
2018-10-31 19:38 ` Igor Stoppa
2018-10-31 10:02 ` Peter Zijlstra
2018-10-31 20:36 ` Andy Lutomirski
2018-10-31 21:00 ` Peter Zijlstra
2018-10-31 22:57 ` Andy Lutomirski
2018-10-31 23:10 ` Igor Stoppa
2018-10-31 23:19 ` Andy Lutomirski
2018-10-31 23:26 ` Igor Stoppa
2018-11-01 8:21 ` Thomas Gleixner
2018-11-01 15:58 ` Igor Stoppa
2018-11-01 17:08 ` Peter Zijlstra
2018-10-30 18:51 ` Andy Lutomirski
2018-10-30 19:14 ` Kees Cook
2018-10-30 21:25 ` Matthew Wilcox
2018-10-30 21:55 ` Igor Stoppa
2018-10-30 22:08 ` Matthew Wilcox
2018-10-31 9:29 ` Peter Zijlstra
2018-10-30 23:18 ` Nadav Amit
2018-10-31 9:08 ` Peter Zijlstra
2018-11-01 16:31 ` Nadav Amit
2018-11-02 21:11 ` Nadav Amit
2018-10-31 9:36 ` Peter Zijlstra
2018-10-31 11:33 ` Matthew Wilcox
2018-11-13 14:25 ` Igor Stoppa
2018-11-13 17:16 ` Andy Lutomirski
2018-11-13 17:43 ` Nadav Amit
2018-11-13 17:47 ` Andy Lutomirski
2018-11-13 18:06 ` Nadav Amit
2018-11-13 18:31 ` Igor Stoppa
2018-11-13 18:33 ` Igor Stoppa
2018-11-13 18:36 ` Andy Lutomirski
2018-11-13 19:03 ` Igor Stoppa
2018-11-21 16:34 ` Igor Stoppa
2018-11-21 17:36 ` Nadav Amit
2018-11-21 18:01 ` Igor Stoppa
2018-11-21 18:15 ` Andy Lutomirski
2018-11-22 19:27 ` Igor Stoppa
2018-11-22 20:04 ` Matthew Wilcox
2018-11-22 20:53 ` Andy Lutomirski
2018-12-04 12:34 ` Igor Stoppa
2018-11-13 18:48 ` Andy Lutomirski
2018-11-13 19:35 ` Igor Stoppa
2018-11-13 18:26 ` Igor Stoppa
2018-11-13 18:35 ` Andy Lutomirski
2018-11-13 19:01 ` Igor Stoppa
2018-10-31 9:27 ` Igor Stoppa
2018-10-26 11:09 ` Markus Heiser
2018-10-29 19:35 ` Igor Stoppa
2018-10-26 15:05 ` Jonathan Corbet
2018-10-29 19:38 ` Igor Stoppa
2018-10-29 20:35 ` Igor Stoppa
2018-10-23 21:34 ` [PATCH 11/17] prmem: llist: use designated initializer Igor Stoppa
2018-10-23 21:34 ` [PATCH 12/17] prmem: linked list: set alignment Igor Stoppa
2018-10-26 9:31 ` Peter Zijlstra
2018-10-23 21:35 ` [PATCH 13/17] prmem: linked list: disable layout randomization Igor Stoppa
2018-10-24 13:43 ` Alexey Dobriyan
2018-10-29 19:40 ` Igor Stoppa
2018-10-26 9:32 ` Peter Zijlstra
2018-10-26 10:17 ` Matthew Wilcox
2018-10-30 15:39 ` Peter Zijlstra
2018-10-23 21:35 ` [PATCH 14/17] prmem: llist, hlist, both plain and rcu Igor Stoppa
2018-10-24 11:37 ` Mathieu Desnoyers
2018-10-24 14:03 ` Igor Stoppa
2018-10-24 14:56 ` Tycho Andersen
2018-10-24 22:52 ` Igor Stoppa
2018-10-25 8:11 ` Tycho Andersen
2018-10-28 9:52 ` Steven Rostedt
2018-10-29 19:43 ` Igor Stoppa
2018-10-26 9:38 ` Peter Zijlstra
2018-10-23 21:35 ` [PATCH 15/17] prmem: test cases for prlist and prhlist Igor Stoppa
2018-10-23 21:35 ` [PATCH 16/17] prmem: pratomic-long Igor Stoppa
2018-10-25 0:13 ` Peter Zijlstra
2018-10-29 21:17 ` Igor Stoppa
2018-10-30 15:58 ` Peter Zijlstra
2018-10-30 16:28 ` Will Deacon
2018-10-31 9:10 ` Peter Zijlstra
2018-11-01 3:28 ` Kees Cook
2018-10-23 21:35 ` [PATCH 17/17] prmem: ima: turn the measurements list write rare Igor Stoppa
2018-10-24 23:03 ` [RFC v1 PATCH 00/17] prmem: protected memory Dave Chinner
2018-10-29 19:47 ` Igor Stoppa
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=20181028183126.GB744@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=corbet@lwn.net \
--cc=dave.hansen@linux.intel.com \
--cc=david@fromorbit.com \
--cc=igor.stoppa@gmail.com \
--cc=igor.stoppa@huawei.com \
--cc=jmorris@namei.org \
--cc=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=labbott@redhat.com \
--cc=linux-doc@vger.kernel.org \
--cc=linux-integrity@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=mhocko@kernel.org \
--cc=rdunlap@infradead.org \
--cc=rppt@linux.vnet.ibm.com \
--cc=willy@infradead.org \
--cc=zohar@linux.vnet.ibm.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).