From: Khalid Aziz <khalid.aziz@oracle.com>
To: Ingo Molnar <mingo@kernel.org>
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 10:49:26 -0600 [thread overview]
Message-ID: <e16c1d73-d361-d9c7-5b8e-c495318c2509@oracle.com> (raw)
In-Reply-To: <20190417161042.GA43453@gmail.com>
On 4/17/19 10:15 AM, Ingo Molnar wrote:
>
> [ Sorry, had to trim the Cc: list from hell. Tried to keep all the
> mailing lists and all x86 developers. ]
>
> * Khalid Aziz <khalid.aziz@oracle.com> wrote:
>
>> From: Juerg Haefliger <juerg.haefliger@canonical.com>
>>
>> This patch adds basic support infrastructure for XPFO which protects
>> against 'ret2dir' kernel attacks. The basic idea is to enforce
>> exclusive ownership of page frames by either the kernel or userspace,
>> unless explicitly requested by the kernel. Whenever a page destined for
>> userspace is allocated, it is unmapped from physmap (the kernel's page
>> table). When such a page is reclaimed from userspace, it is mapped back
>> to physmap. Individual architectures can enable full XPFO support using
>> this infrastructure by supplying architecture specific pieces.
>
> I have a higher level, meta question:
>
> Is there any updated analysis outlining why this XPFO overhead would be
> required on x86-64 kernels running on SMAP/SMEP CPUs which should be all
> recent Intel and AMD CPUs, and with kernel that mark all direct kernel
> mappings as non-executable - which should be all reasonably modern
> kernels later than v4.0 or so?
>
> 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.
Thanks,
Khalid
next prev parent reply other threads:[~2019-04-17 16:51 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1554248001.git.khalid.aziz@oracle.com>
[not found] ` <e6c57f675e5b53d4de266412aa526b7660c47918.1554248002.git.khalid.aziz@oracle.com>
[not found] ` <CALCETrXvwuwkVSJ+S5s7wTBkNNj3fRVxpx9BvsXWrT=3ZdRnCw@mail.gmail.com>
[not found] ` <20190404013956.GA3365@cisco>
[not found] ` <CALCETrVp37Xo3EMHkeedP1zxUMf9og=mceBa8c55e1F4G1DRSQ@mail.gmail.com>
[not found] ` <20190404154727.GA14030@cisco>
2019-04-04 16:23 ` [RFC PATCH v9 02/13] x86: always set IF before oopsing from page fault Sebastian Andrzej Siewior
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
[not found] ` <f1ac3700970365fb979533294774af0b0dd84b3b.1554248002.git.khalid.aziz@oracle.com>
2019-04-17 16:15 ` [RFC PATCH v9 03/13] mm: Add support for eXclusive Page Frame Ownership (XPFO) Ingo Molnar
2019-04-17 16:49 ` Khalid Aziz [this message]
2019-04-17 17:09 ` Ingo Molnar
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
[not found] ` <CAHk-=wgBMg9P-nYQR2pS0XwVdikPCBqLsMFqR9nk=wSmAd4_5g@mail.gmail.com>
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
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