netdev - Re: [PATCH] lsm: make security_socket_getpeersec_stream() sockptr

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Date:   Fri, 28 Oct 2022 06:32:39 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     John Johansen <john.johansen@...onical.com>
Cc:     linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
        netdev@...r.kernel.org,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH] lsm: make security_socket_getpeersec_stream() sockptr_t safe

On Thu, Oct 20, 2022 at 11:10 AM Paul Moore <paul@...l-moore.com> wrote:
> On Thu, Oct 20, 2022 at 9:16 AM Casey Schaufler <casey@...aufler-ca.com> wrote:
> > On 10/10/2022 2:58 PM, Paul Moore wrote:
> > > Commit 4ff09db1b79b ("bpf: net: Change sk_getsockopt() to take the
> > > sockptr_t argument") made it possible to call sk_getsockopt()
> > > with both user and kernel address space buffers through the use of
> > > the sockptr_t type.  Unfortunately at the time of conversion the
> > > security_socket_getpeersec_stream() LSM hook was written to only
> > > accept userspace buffers, and in a desire to avoid having to change
> > > the LSM hook the commit author simply passed the sockptr_t's
> > > userspace buffer pointer.  Since the only sk_getsockopt() callers
> > > at the time of conversion which used kernel sockptr_t buffers did
> > > not allow SO_PEERSEC, and hence the
> > > security_socket_getpeersec_stream() hook, this was acceptable but
> > > also very fragile as future changes presented the possibility of
> > > silently passing kernel space pointers to the LSM hook.
> > >
> > > There are several ways to protect against this, including careful
> > > code review of future commits, but since relying on code review to
> > > catch bugs is a recipe for disaster and the upstream eBPF maintainer
> > > is "strongly against defensive programming", this patch updates the
> > > LSM hook, and all of the implementations to support sockptr_t and
> > > safely handle both user and kernel space buffers.
> > >
> > > Signed-off-by: Paul Moore <paul@...l-moore.com>
> >
> > Smack part looks ok, I haven't had the opportunity to test it.
> > Will do so as I crunch through the backlog.
> >
> > Acked-by: Casey Schaufler <casey@...aufler-ca.com>
>
> Thanks Casey.
>
> John, how do the AppArmor parts look?

Hey John - can you weigh in on the AppArmor bits?

> > > ---
> > >  include/linux/lsm_hook_defs.h |    2 +-
> > >  include/linux/lsm_hooks.h     |    4 ++--
> > >  include/linux/security.h      |   11 +++++++----
> > >  net/core/sock.c               |    3 ++-
> > >  security/apparmor/lsm.c       |   29 +++++++++++++----------------
> > >  security/security.c           |    6 +++---
> > >  security/selinux/hooks.c      |   13 ++++++-------
> > >  security/smack/smack_lsm.c    |   19 ++++++++++---------
> > >  8 files changed, 44 insertions(+), 43 deletions(-)

-- 
paul-moore.com