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From:   =?UTF-8?Q?Christian_G=C3=B6ttsche?= <cgzones@googlemail.com>
Date:   Mon, 2 May 2022 15:45:35 +0200
Message-ID: <CAJ2a_DeT6AG0jp4gTdsEy7nh=s6cLR7QCsYXAz2+3vsdRKxddg@mail.gmail.com>
Subject: Re: [RFC PATCH] mm: create security context for memfd_secret inodes
To:     Paul Moore <paul@paul-moore.com>
Cc:     SElinux list <selinux@vger.kernel.org>,
        James Morris <jmorris@namei.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        linux-security-module@vger.kernel.org,
        Stephen Smalley <stephen.smalley.work@gmail.com>,
        Eric Paris <eparis@parisplace.org>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        Linux kernel mailing list <linux-kernel@vger.kernel.org>
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On Thu, 17 Feb 2022 at 23:32, Paul Moore <paul@paul-moore.com> wrote:
>
> On Thu, Feb 17, 2022 at 9:24 AM Christian G=C3=B6ttsche
> <cgzones@googlemail.com> wrote:
> > On Thu, 27 Jan 2022 at 00:01, Paul Moore <paul@paul-moore.com> wrote:
> > > On Tue, Jan 25, 2022 at 9:33 AM Christian G=C3=B6ttsche
> > > <cgzones@googlemail.com> wrote:
> > > >
> > > > Create a security context for the inodes created by memfd_secret(2)=
 via
> > > > the LSM hook inode_init_security_anon to allow a fine grained contr=
ol.
> > > > As secret memory areas can affect hibernation and have a global sha=
red
> > > > limit access control might be desirable.
> > > >
> > > > Signed-off-by: Christian G=C3=B6ttsche <cgzones@googlemail.com>
> > > > ---
> > > > An alternative way of checking memfd_secret(2) is to create a new L=
SM
> > > > hook and e.g. for SELinux check via a new process class permission.
> > > > ---
> > > >  mm/secretmem.c | 9 +++++++++
> > > >  1 file changed, 9 insertions(+)
> > >
> > > This seems reasonable to me, and I like the idea of labeling the anon
> > > inode as opposed to creating a new set of LSM hooks.  If we want to
> > > apply access control policy to the memfd_secret() fds we are going to
> > > need to attach some sort of LSM state to the inode, we might as well
> > > use the mechanism we already have instead of inventing another one.
> >
> > Any further comments (on design or implementation)?
> >
> > Should I resend a non-rfc?
>
> I personally would really like to see a selinux-testsuite for this so
> that we can verify it works not just now but in the future too.  I
> think having a test would also help demonstrate the usefulness of the
> additional LSM controls.
>

Any comments (especially from the mm people)?

Draft SELinux testsuite patch:
https://github.com/SELinuxProject/selinux-testsuite/pull/80

> > One naming question:
> > Should the anonymous inode class be named "[secretmem]", like
> > "[userfaultfd]", or "[secret_mem]" similar to "[io_uring]"?
>
> The pr_fmt() string in mm/secretmem.c uses "secretmem" so I would
> suggest sticking with "[secretmem]", although that is question best
> answered by the secretmem maintainer.
>
> --
> paul-moore.com