Re: [PATCH v3 0/7] User namespace mount updates

From	Seth Forshee <seth.forshee@canonical.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3 0/7] User namespace mount updates
Date	2015-11-17 20:20 +0100
Message-ID	<qvTXk-J9-19@gated-at.bofh.it> (permalink)
References	<qvRC9-7wq-11@gated-at.bofh.it> <qvRVv-7TO-11@gated-at.bofh.it> <qvSeT-81H-29@gated-at.bofh.it> <qvSHV-8dG-19@gated-at.bofh.it> <qvTND-EM-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, Nov 17, 2015 at 02:02:09PM -0500, Austin S Hemmelgarn wrote:
> On 2015-11-17 12:55, Al Viro wrote:
> >On Tue, Nov 17, 2015 at 11:25:51AM -0600, Seth Forshee wrote:
> >
> >>Shortly after that I plan to follow with support for ext4. I've been
> >>fuzzing ext4 for a while now and it has held up well, and I'm currently
> >>working on hand-crafted attacks. Ted has commented privately (to others,
> >>not to me personally) that he will fix bugs for such attacks, though I
> >>haven't seen any public comments to that effect.
> >
> >_Static_ attacks, or change-image-under-mounted-fs attacks?
> To properly protect against attacks on mounted filesystems, we'd
> need some new concept of a userspace immutable file (that is, one
> where nobody can write to it except the kernel, and only the kernel
> can change it between regular access and this new state), and then
> have the kernel set an image (or block device) to this state when a
> filesystem is mounted from it (this introduces all kinds of other
> issues too however, for example stuff that allows an online fsck on
> the device will stop working, as will many un-deletion tools).

Yeah, Serge and I were just tossing that idea around on irc. If we can
make that work then it's probably the best solution.

From a naive perspective it seems like all we really have to do is make
the block device inode immutable to userspace when it is mounted. And
the parent block device if it's a partition, which might be a bit
troublesome. We'd have to ensure that writes couldn't happen via any fds
already open when the device was mounted too.

We'd need some cooperation from the loop driver too I suppose, to make
sure the file backing the loop device is also immutable.

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Thread

[PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-17 17:50 +0100
  [PATCH v3 1/7] block_dev: Support checking inode permissions in lookup_bdev() Seth Forshee <seth.forshee@canonical.com> - 2015-11-17 17:50 +0100
  [PATCH v3 2/7] block_dev: Check permissions towards block device inode when mounting Seth Forshee <seth.forshee@canonical.com> - 2015-11-17 17:50 +0100
  [PATCH v3 3/7] mtd: Check permissions towards mtd block device inode when mounting Seth Forshee <seth.forshee@canonical.com> - 2015-11-17 17:50 +0100
  Re: [PATCH v3 0/7] User namespace mount updates Al Viro <viro@ZenIV.linux.org.uk> - 2015-11-17 18:10 +0100
    Re: [PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-17 18:30 +0100
      Re: [PATCH v3 0/7] User namespace mount updates "Serge E. Hallyn" <serge@hallyn.com> - 2015-11-17 18:50 +0100
      Re: [PATCH v3 0/7] User namespace mount updates Al Viro <viro@ZenIV.linux.org.uk> - 2015-11-17 19:00 +0100
        Re: [PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-17 19:40 +0100
          Re: [PATCH v3 0/7] User namespace mount updates Richard Weinberger <richard.weinberger@gmail.com> - 2015-11-17 20:20 +0100
            Re: [PATCH v3 0/7] User namespace mount updates Octavian Purdila <octavian.purdila@intel.com> - 2015-11-17 20:30 +0100
              Re: [PATCH v3 0/7] User namespace mount updates Richard Weinberger <richard@nod.at> - 2015-11-17 21:20 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Octavian Purdila <octavian.purdila@intel.com> - 2015-11-17 23:10 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-19 16:30 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Octavian Purdila <octavian.purdila@intel.com> - 2015-11-19 17:20 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-19 17:40 +0100
                Re: [PATCH v3 0/7] User namespace mount updates "Serge E. Hallyn" <serge.hallyn@ubuntu.com> - 2015-11-20 18:40 +0100
            Re: [PATCH v3 0/7] User namespace mount updates Richard Weinberger <richard@nod.at> - 2015-11-17 20:30 +0100
            Re: [PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-17 20:30 +0100
          Re: [PATCH v3 0/7] User namespace mount updates Theodore Ts'o <tytso@mit.edu> - 2015-11-18 20:20 +0100
            Re: [PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-18 20:30 +0100
            Re: [PATCH v3 0/7] User namespace mount updates Serge Hallyn <serge.hallyn@ubuntu.com> - 2015-11-18 20:40 +0100
        Re: [PATCH v3 0/7] User namespace mount updates Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-11-17 20:10 +0100
          Re: [PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-17 20:20 +0100
            Re: [PATCH v3 0/7] User namespace mount updates Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-11-17 22:00 +0100
              Re: [PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-17 22:40 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-11-18 13:30 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-18 15:30 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Al Viro <viro@ZenIV.linux.org.uk> - 2015-11-18 16:00 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-18 16:10 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Al Viro <viro@ZenIV.linux.org.uk> - 2015-11-18 16:20 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Richard Weinberger <richard.weinberger@gmail.com> - 2015-11-18 16:30 +0100
                Re: [PATCH v3 0/7] User namespace mount updates James Morris <jmorris@namei.org> - 2015-11-19 08:50 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Richard Weinberger <richard@nod.at> - 2015-11-19 09:00 +0100
                Re: [PATCH v3 0/7] User namespace mount updates "Serge E. Hallyn" <serge.hallyn@ubuntu.com> - 2015-11-19 15:30 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Richard Weinberger <richard@nod.at> - 2015-11-19 16:10 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Colin Walters <walters@verbum.org> - 2015-11-19 15:40 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Richard Weinberger <richard@nod.at> - 2015-11-19 15:50 +0100
                Re: [PATCH v3 0/7] User namespace mount updates "Richard W.M. Jones" <rjones@redhat.com> - 2015-11-19 16:20 +0100
                Re: [PATCH v3 0/7] User namespace mount updates "Serge E. Hallyn" <serge.hallyn@ubuntu.com> - 2015-11-19 16:00 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Nikolay Borisov <kernel@kyup.com> - 2015-11-18 16:40 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-11-18 16:40 +0100
          Re: [PATCH v3 0/7] User namespace mount updates Al Viro <viro@ZenIV.linux.org.uk> - 2015-11-17 20:40 +0100
            Re: [PATCH v3 0/7] User namespace mount updates Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-11-17 21:40 +0100
              Re: [PATCH v3 0/7] User namespace mount updates Al Viro <viro@ZenIV.linux.org.uk> - 2015-11-17 22:10 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-17 23:10 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-11-18 13:50 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Seth Forshee <seth.forshee@canonical.com> - 2015-11-18 15:40 +0100
                Re: [PATCH v3 0/7] User namespace mount updates Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-11-18 16:40 +0100
            Re: [PATCH v3 0/7] User namespace mount updates bfields@fieldses.org (J. Bruce Fields) - 2015-11-18 19:50 +0100

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