From: Ingo Molnar <mingo@kernel.org>
To: Khalid Aziz <khalid.aziz@oracle.com>
Cc: juergh@gmail.com, tycho@tycho.ws, jsteckli@amazon.de,
keescook@google.com, konrad.wilk@oracle.com,
Juerg Haefliger <juerg.haefliger@canonical.com>,
deepa.srinivasan@oracle.com, chris.hyser@oracle.com,
tyhicks@canonical.com, dwmw@amazon.co.uk,
andrew.cooper3@citrix.com, jcm@redhat.com,
boris.ostrovsky@oracle.com, iommu@lists.linux-foundation.org,
x86@kernel.org, linux-arm-kernel@lists.infradead.org,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-security-module@vger.kernel.org,
Khalid Aziz <khalid@gonehiking.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Dave Hansen <dave@sr71.net>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Arjan van de Ven <arjan@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [RFC PATCH v9 03/13] mm: Add support for eXclusive Page Frame Ownership (XPFO)
Date: Wed, 17 Apr 2019 19:09:18 +0200 [thread overview]
Message-ID: <20190417170918.GA68678@gmail.com> (raw)
In-Reply-To: <e16c1d73-d361-d9c7-5b8e-c495318c2509@oracle.com>
* Khalid Aziz <khalid.aziz@oracle.com> wrote:
> > I.e. the original motivation of the XPFO patches was to prevent execution
> > of direct kernel mappings. Is this motivation still present if those
> > mappings are non-executable?
> >
> > (Sorry if this has been asked and answered in previous discussions.)
>
> Hi Ingo,
>
> That is a good question. Because of the cost of XPFO, we have to be very
> sure we need this protection. The paper from Vasileios, Michalis and
> Angelos - <http://www.cs.columbia.edu/~vpk/papers/ret2dir.sec14.pdf>,
> does go into how ret2dir attacks can bypass SMAP/SMEP in sections 6.1
> and 6.2.
So it would be nice if you could generally summarize external arguments
when defending a patchset, instead of me having to dig through a PDF
which not only causes me to spend time that you probably already spent
reading that PDF, but I might also interpret it incorrectly. ;-)
The PDF you cited says this:
"Unfortunately, as shown in Table 1, the W^X prop-erty is not enforced
in many platforms, including x86-64. In our example, the content of
user address 0xBEEF000 is also accessible through kernel address
0xFFFF87FF9F080000 as plain, executable code."
Is this actually true of modern x86-64 kernels? We've locked down W^X
protections in general.
I.e. this conclusion:
"Therefore, by simply overwriting kfptr with 0xFFFF87FF9F080000 and
triggering the kernel to dereference it, an attacker can directly
execute shell code with kernel privileges."
... appears to be predicated on imperfect W^X protections on the x86-64
kernel.
Do such holes exist on the latest x86-64 kernel? If yes, is there a
reason to believe that these W^X holes cannot be fixed, or that any fix
would be more expensive than XPFO?
Thanks,
Ingo
next prev parent reply other threads:[~2019-04-17 17:09 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-03 17:34 [RFC PATCH v9 00/13] Add support for eXclusive Page Frame Ownership Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 01/13] mm: add MAP_HUGETLB support to vm_mmap Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 02/13] x86: always set IF before oopsing from page fault Khalid Aziz
2019-04-04 0:12 ` Andy Lutomirski
2019-04-04 1:42 ` Tycho Andersen
2019-04-04 4:12 ` Andy Lutomirski
2019-04-04 15:47 ` Tycho Andersen
2019-04-04 16:23 ` Sebastian Andrzej Siewior
2019-04-04 16:28 ` Thomas Gleixner
2019-04-04 17:11 ` Andy Lutomirski
2019-04-03 17:34 ` [RFC PATCH v9 03/13] mm: Add support for eXclusive Page Frame Ownership (XPFO) Khalid Aziz
2019-04-04 7:21 ` Peter Zijlstra
2019-04-04 9:25 ` Peter Zijlstra
2019-04-04 14:48 ` Tycho Andersen
2019-04-04 7:43 ` Peter Zijlstra
2019-04-04 15:15 ` Khalid Aziz
2019-04-04 17:01 ` Peter Zijlstra
2019-04-17 16:15 ` Ingo Molnar
2019-04-17 16:49 ` Khalid Aziz
2019-04-17 17:09 ` Ingo Molnar [this message]
2019-04-17 17:19 ` Nadav Amit
2019-04-17 17:26 ` Ingo Molnar
2019-04-17 17:44 ` Nadav Amit
2019-04-17 21:19 ` Thomas Gleixner
2019-04-17 23:18 ` Linus Torvalds
2019-04-17 23:42 ` Thomas Gleixner
2019-04-17 23:52 ` Linus Torvalds
2019-04-18 4:41 ` Andy Lutomirski
2019-04-18 5:41 ` Kees Cook
2019-04-18 14:34 ` Khalid Aziz
2019-04-22 19:30 ` Khalid Aziz
2019-04-22 22:23 ` Kees Cook
2019-04-18 6:14 ` Thomas Gleixner
2019-04-17 17:33 ` Khalid Aziz
2019-04-17 19:49 ` Andy Lutomirski
2019-04-17 19:52 ` Tycho Andersen
2019-04-17 20:12 ` Khalid Aziz
2019-05-01 14:49 ` Waiman Long
2019-05-01 15:18 ` Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 04/13] xpfo, x86: Add support for XPFO for x86-64 Khalid Aziz
2019-04-04 7:52 ` Peter Zijlstra
2019-04-04 15:40 ` Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 05/13] mm: add a user_virt_to_phys symbol Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 06/13] lkdtm: Add test for XPFO Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 07/13] arm64/mm: Add support " Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 08/13] swiotlb: Map the buffer if it was unmapped by XPFO Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 09/13] xpfo: add primitives for mapping underlying memory Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 10/13] arm64/mm, xpfo: temporarily map dcache regions Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 11/13] xpfo, mm: optimize spinlock usage in xpfo_kunmap Khalid Aziz
2019-04-04 7:56 ` Peter Zijlstra
2019-04-04 16:06 ` Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 12/13] xpfo, mm: Defer TLB flushes for non-current CPUs (x86 only) Khalid Aziz
2019-04-04 4:10 ` Andy Lutomirski
[not found] ` <91f1dbce-332e-25d1-15f6-0e9cfc8b797b@oracle.com>
2019-04-05 7:17 ` Thomas Gleixner
2019-04-05 14:44 ` Dave Hansen
2019-04-05 15:24 ` Andy Lutomirski
2019-04-05 15:56 ` Tycho Andersen
2019-04-05 16:32 ` Andy Lutomirski
2019-04-05 15:56 ` Khalid Aziz
2019-04-05 16:01 ` Dave Hansen
2019-04-05 16:27 ` Andy Lutomirski
2019-04-05 16:41 ` Peter Zijlstra
2019-04-05 17:35 ` Khalid Aziz
2019-04-05 15:44 ` Khalid Aziz
2019-04-05 15:24 ` Andy Lutomirski
2019-04-04 8:18 ` Peter Zijlstra
2019-04-03 17:34 ` [RFC PATCH v9 13/13] xpfo, mm: Optimize XPFO TLB flushes by batching them together Khalid Aziz
2019-04-04 16:44 ` [RFC PATCH v9 00/13] Add support for eXclusive Page Frame Ownership Nadav Amit
2019-04-04 17:18 ` Khalid Aziz
2019-04-06 6:40 ` Jon Masters
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