From: Ondrej Mosnacek <omosnace@redhat.com>
To: Casey Schaufler <casey@schaufler-ca.com>
Cc: Linux Security Module list
<linux-security-module@vger.kernel.org>,
James Morris <jmorris@namei.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
Stephen Smalley <stephen.smalley.work@gmail.com>,
SElinux list <selinux@vger.kernel.org>,
linuxppc-dev@lists.ozlabs.org,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
bpf <bpf@vger.kernel.org>, network dev <netdev@vger.kernel.org>,
Linux kernel mailing list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] lockdown,selinux: fix bogus SELinux lockdown permission checks
Date: Wed, 12 May 2021 15:21:37 +0200 [thread overview]
Message-ID: <CAFqZXNtr1YjzRg7fTm+j=0oZF+7C5xEu5J0mCZynP-dgEzvyUg@mail.gmail.com> (raw)
In-Reply-To: <a8d138a6-1d34-1457-9266-4abeddb6fdba@schaufler-ca.com>
On Sat, May 8, 2021 at 12:17 AM Casey Schaufler <casey@schaufler-ca.com> wrote:
> On 5/7/2021 4:40 AM, Ondrej Mosnacek wrote:
> > Commit 59438b46471a ("security,lockdown,selinux: implement SELinux
> > lockdown") added an implementation of the locked_down LSM hook to
> > SELinux, with the aim to restrict which domains are allowed to perform
> > operations that would breach lockdown.
> >
> > However, in several places the security_locked_down() hook is called in
> > situations where the current task isn't doing any action that would
> > directly breach lockdown, leading to SELinux checks that are basically
> > bogus.
> >
> > Since in most of these situations converting the callers such that
> > security_locked_down() is called in a context where the current task
> > would be meaningful for SELinux is impossible or very non-trivial (and
> > could lead to TOCTOU issues for the classic Lockdown LSM
> > implementation), fix this by adding a separate hook
> > security_locked_down_globally()
>
> This is a poor solution to the stated problem. Rather than adding
> a new hook you should add the task as a parameter to the existing hook
> and let the security modules do as they will based on its value.
> If the caller does not have an appropriate task it should pass NULL.
> The lockdown LSM can ignore the task value and SELinux can make its
> own decision based on the task value passed.
The problem with that approach is that all callers would then need to
be updated and I intended to keep the patch small as I'd like it to go
to stable kernels as well.
But it does seem to be a better long-term solution - would it work for
you (and whichever maintainer would be taking the patch(es)) if I just
added another patch that refactors it to use the task parameter?
--
Ondrej Mosnacek
Software Engineer, Linux Security - SELinux kernel
Red Hat, Inc.
next prev parent reply other threads:[~2021-05-12 13:21 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-07 11:40 [PATCH] lockdown,selinux: fix bogus SELinux lockdown permission checks Ondrej Mosnacek
2021-05-07 22:17 ` Casey Schaufler
2021-05-12 13:21 ` Ondrej Mosnacek [this message]
2021-05-12 16:17 ` Casey Schaufler
2021-05-12 16:44 ` Ondrej Mosnacek
2021-05-12 17:12 ` Casey Schaufler
2021-05-14 15:12 ` Ondrej Mosnacek
2021-05-15 0:57 ` Casey Schaufler
2021-05-17 8:34 ` Ondrej Mosnacek
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