From: Jonathan Corbet <corbet@lwn.net>
To: Peter Xu <peterx@redhat.com>
Cc: Daniel Colascione <dancol@google.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Luis Chamberlain <mcgrof@kernel.org>,
Kees Cook <keescook@chromium.org>,
Iurii Zaikin <yzaikin@google.com>,
Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Shevchenko <andy.shevchenko@gmail.com>,
Vlastimil Babka <vbabka@suse.cz>,
Mel Gorman <mgorman@techsingularity.net>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Andrea Arcangeli <aarcange@redhat.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Jerome Glisse <jglisse@redhat.com>, Shaohua Li <shli@fb.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, timmurray@google.com,
minchan@google.com, sspatil@google.com, lokeshgidra@google.com
Subject: Re: [PATCH 2/2] Add a new sysctl knob: unprivileged_userfaultfd_user_mode_only
Date: Thu, 7 May 2020 13:15:03 -0600 [thread overview]
Message-ID: <20200507131503.02aba5a6@lwn.net> (raw)
In-Reply-To: <20200506193816.GB228260@xz-x1>
On Wed, 6 May 2020 15:38:16 -0400
Peter Xu <peterx@redhat.com> wrote:
> If this is going to be added... I am thinking whether it should be easier to
> add another value for unprivileged_userfaultfd, rather than a new sysctl. E.g.:
>
> "0": unprivileged userfaultfd forbidden
> "1": unprivileged userfaultfd allowed (both user/kernel faults)
> "2": unprivileged userfaultfd allowed (only user faults)
>
> Because after all unprivileged_userfaultfd_user_mode_only will be meaningless
> (iiuc) if unprivileged_userfaultfd=0. The default value will also be the same
> as before ("1") then.
It occurs to me to wonder whether this interface should also let an admin
block *privileged* user from handling kernel-space faults? In a
secure-boot/lockdown setting, this could be a hardening measure that keeps
a (somewhat) restricted root user from expanding their privilege...?
jon
next prev parent reply other threads:[~2020-05-07 19:15 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-23 0:26 [PATCH 0/2] Control over userfaultfd kernel-fault handling Daniel Colascione
2020-04-23 0:26 ` [PATCH 1/2] Add UFFD_USER_MODE_ONLY Daniel Colascione
2020-07-24 14:28 ` Michael S. Tsirkin
2020-07-24 14:46 ` Lokesh Gidra
2020-07-26 10:09 ` Michael S. Tsirkin
2020-04-23 0:26 ` [PATCH 2/2] Add a new sysctl knob: unprivileged_userfaultfd_user_mode_only Daniel Colascione
2020-05-06 19:38 ` Peter Xu
2020-05-07 19:15 ` Jonathan Corbet [this message]
2020-05-20 4:06 ` Andrea Arcangeli
2020-05-08 16:52 ` Michael S. Tsirkin
2020-05-08 16:54 ` Michael S. Tsirkin
2020-05-20 4:59 ` Andrea Arcangeli
2020-05-20 18:03 ` Kees Cook
2020-05-20 19:48 ` Andrea Arcangeli
2020-05-20 19:51 ` Andrea Arcangeli
2020-05-20 20:17 ` Lokesh Gidra
2020-05-20 21:16 ` Andrea Arcangeli
2020-07-17 12:57 ` Jeffrey Vander Stoep
2020-07-23 17:30 ` Lokesh Gidra
2020-07-24 0:13 ` Nick Kralevich
2020-07-24 13:40 ` Michael S. Tsirkin
2020-08-06 0:43 ` Nick Kralevich
2020-08-06 5:44 ` Michael S. Tsirkin
2020-08-17 22:11 ` Lokesh Gidra
2020-09-04 3:34 ` Andrea Arcangeli
2020-09-05 0:36 ` Lokesh Gidra
2020-09-19 18:14 ` Nick Kralevich
2020-07-24 14:01 ` [PATCH 0/2] Control over userfaultfd kernel-fault handling Michael S. Tsirkin
2020-07-24 14:41 ` Lokesh Gidra
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