From: Martin Schwidefsky <schwidefsky@de.ibm.com>
To: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
kvm@vger.kernel.org, Heiko Carstens <heiko.carstens@de.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Cornelia Huck <cohuck@redhat.com>,
David Hildenbrand <david@redhat.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jon Masters <jcm@redhat.com>, Marcus Meissner <meissner@suse.de>,
Jiri Kosina <jkosina@suse.cz>,
w@1wt.eu, keescook@chromium.org
Subject: Re: [PATCH 1/5] prctl: add PR_ISOLATE_BP process control
Date: Wed, 24 Jan 2018 07:29:53 +0100 [thread overview]
Message-ID: <20180124072953.50851fec@mschwideX1> (raw)
In-Reply-To: <20180123170719.GA4154@isilmar-4.linta.de>
On Tue, 23 Jan 2018 18:07:19 +0100
Dominik Brodowski <linux@dominikbrodowski.net> wrote:
> On Tue, Jan 23, 2018 at 02:07:01PM +0100, Martin Schwidefsky wrote:
> > Add the PR_ISOLATE_BP operation to prctl. The effect of the process
> > control is to make all branch prediction entries created by the execution
> > of the user space code of this task not applicable to kernel code or the
> > code of any other task.
>
> What is the rationale for requiring a per-process *opt-in* for this added
> protection?
>
> For KPTI on x86, the exact opposite approach is being discussed (see, e.g.
> http://lkml.kernel.org/r/1515612500-14505-1-git-send-email-w@1wt.eu ): By
> default, play it safe, with KPTI enabled. But for "trusted" processes, one
> may opt out using prctrl.
The rationale is that there are cases where you got code from *somewhere*
and want to run it in an isolated context. Think: a docker container that
runs under KVM. But with spectre this is still not really safe. So you
include a wrapper program in the docker container to use the trap door
prctl to start the potential malicious program. Now you should be good, no?
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
next prev parent reply other threads:[~2018-01-24 6:29 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-23 13:07 [RFC][PATCH 0/5] s390: improve speculative execution handling v2 Martin Schwidefsky
2018-01-23 13:07 ` [PATCH 1/5] prctl: add PR_ISOLATE_BP process control Martin Schwidefsky
2018-01-23 17:07 ` Dominik Brodowski
2018-01-24 6:29 ` Martin Schwidefsky [this message]
2018-01-24 8:37 ` Avoiding information leaks between users and between processes by default? [Was: : [PATCH 1/5] prctl: add PR_ISOLATE_BP process control] Dominik Brodowski
2018-01-24 9:24 ` David Woodhouse
2018-01-24 11:15 ` Pavel Machek
2018-01-24 12:48 ` Martin Schwidefsky
2018-01-24 19:01 ` Pavel Machek
2018-01-24 20:46 ` Alan Cox
2018-01-29 13:14 ` Pavel Machek
2018-01-29 20:12 ` Alan Cox
2018-01-24 15:42 ` Alan Cox
2018-01-24 8:08 ` [PATCH 1/5] prctl: add PR_ISOLATE_BP process control Christian Borntraeger
2018-01-23 13:07 ` [PATCH 2/5] s390/alternative: use a copy of the facility bit mask Martin Schwidefsky
2018-01-23 13:59 ` Cornelia Huck
2018-01-23 14:40 ` Martin Schwidefsky
2018-01-23 15:04 ` Cornelia Huck
2018-01-23 13:07 ` [PATCH 3/5] s390: add options to change branch prediction behaviour for the kernel Martin Schwidefsky
2018-01-23 13:07 ` [PATCH 4/5] s390: define ISOLATE_BP to run tasks with modified branch prediction Martin Schwidefsky
2018-01-23 14:21 ` Christian Borntraeger
2018-01-23 20:32 ` Radim Krčmář
2018-01-24 6:36 ` Martin Schwidefsky
2018-01-24 11:50 ` Radim Krčmář
2018-01-23 13:07 ` [PATCH 5/5] s390: scrub registers on kernel entry and KVM exit Martin Schwidefsky
2018-01-23 13:09 ` Christian Borntraeger
2018-01-23 14:32 ` Martin Schwidefsky
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