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From: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	X86 ML <x86@kernel.org>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	Andy Lutomirski <luto@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Borislav Petkov <bp@suse.de>, Brian Gerst <brgerst@gmail.com>,
	Chen Yucong <slaoub@gmail.com>,
	Chris Metcalf <cmetcalf@mellanox.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Fenghua Yu <fenghua.yu@intel.com>, Huang Rui <ray.huang@amd.com>,
	Jiri Slaby <jslaby@suse.cz>, Jonathan Corbet <corbet@lwn.net>,
	"Michael S . Tsirkin" <mst@redhat.com>,
	Paul Gortmaker <paul.gortmaker@windriver.com>,
	"Ravi V . Shankar" <ravi.v.shankar@intel.com>,
	Vlastimil Babka <vbabka@suse.cz>, Shuah Khan <shuah@kernel.org>
Subject: Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention
Date: Tue, 08 Nov 2016 20:31:29 -0800	[thread overview]
Message-ID: <1478665889.2533.8.camel@ranerica-desktop> (raw)
In-Reply-To: <CALCETrV+c4Rw9zbB3=Jc2F6jtxib3prxNqMXgnUSyMc5QnU9fA@mail.gmail.com>

On Tue, 2016-11-08 at 07:34 -0800, Andy Lutomirski wrote:
> > Would it not be better to emulate these instructions for them? What
> way
> > we can verify they're not malicious.
> 
> Forget malice -- if they are really needed for some silly vm86-using
> program, let's trap them and emulate them so they return dummy values.
> 
> Also, keep in mind that vm86 is already effectively gated behind a
> sysctl for non-root.  I think the default should be that, if root has
> enabled vm86, it should work.

Then should I keep UMIP enabled by default and still provide an option
to disable it via a kernel parameter?

Also, a third option, umip=novm86 would "disable" UMIP in vm86 tasks.
Under the new approach (of emulating the impacted instructions), this
option, a #GP fault would still be generated but the actual values of
GDT/LDT/IDT/MSW would be passed to user space. Does this make sense?

Thanks and BR,
Ricardo

  parent reply	other threads:[~2016-11-09  4:31 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-11-08  6:12 [PATCH 0/4] x86: enable User-Mode Instruction Prevention Ricardo Neri
2016-11-08  6:12 ` [PATCH 1/4] x86/cpufeature: Add User-Mode Instruction Prevention definitions Ricardo Neri
2016-11-08 15:32   ` Andy Lutomirski
2016-11-09  4:25     ` Ricardo Neri
2016-11-09 11:02       ` Andy Lutomirski
2016-11-10  3:24         ` Ricardo Neri
2016-11-10  8:58           ` Borislav Petkov
2016-11-11  4:08             ` Ricardo Neri
2016-11-11 10:22               ` Borislav Petkov
2016-11-12  1:24                 ` Ricardo Neri
2016-11-11 18:06               ` Dave Hansen
2016-11-10 17:09           ` Dave Hansen
2016-11-08  6:12 ` [PATCH 2/4] x86: Prepare vm86 tasks to handle User-Mode Instruction Prevention Ricardo Neri
2016-11-08 16:01   ` Andy Lutomirski
2016-11-08 17:00     ` Peter Zijlstra
2016-11-09  4:26       ` Ricardo Neri
2016-11-08  6:12 ` [PATCH 3/4] x86: Enable " Ricardo Neri
2016-11-08  6:12 ` [PATCH 4/4] selftests/x86: Add tests for " Ricardo Neri
2016-11-08 13:16 ` [PATCH 0/4] x86: enable " Peter Zijlstra
2016-11-08 15:34   ` Andy Lutomirski
2016-11-08 16:52     ` Thomas Gleixner
2016-11-09  4:26       ` Ricardo Neri
2016-11-09  4:31     ` Ricardo Neri [this message]
2016-11-09 11:05       ` Andy Lutomirski
2016-11-10  6:46         ` Ricardo Neri
2016-11-10  8:52           ` Stas Sergeev
2016-11-11  4:14             ` Ricardo Neri
2016-11-11 20:51               ` Stas Sergeev
2016-11-12  1:29                 ` Ricardo Neri
2016-11-14 10:59           ` One Thousand Gnomes
2016-11-14 18:36             ` Harald Arnesen

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