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

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Message-ID: <CAHC9VhQr_deuGRCien23zso+gi0VHUHK8ayYK6sBxmK3DyBOjg@mail.gmail.com>
Date:   Thu, 20 Oct 2022 11:10:03 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Casey Schaufler <casey@...aufler-ca.com>,
        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>
Subject: Re: [PATCH] lsm: make security_socket_getpeersec_stream() sockptr_t safe

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?

> > ---
> >  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