Re: [PATCH] selinux: vsock: Set SID for socket returned by accept()

From: David Brazdil <dbrazdil@google.com>
To: Paul Moore <paul@paul-moore.com>
Cc: selinux@vger.kernel.org, linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org, linux-security-module@vger.kernel.org,
	"David S . Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	James Morris <jmorris@namei.org>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	Stephen Smalley <stephen.smalley.work@gmail.com>,
	Eric Paris <eparis@parisplace.org>,
	Kees Cook <keescook@chromium.org>,
	Jeff Vander Stoep <jeffv@google.com>,
	Alistair Delva <adelva@google.com>
Subject: Re: [PATCH] selinux: vsock: Set SID for socket returned by accept()
Date: Fri, 19 Mar 2021 12:57:16 +0000	[thread overview]
Message-ID: <YFSfrIZAz6zHENT7@google.com> (raw)
In-Reply-To: <CAHC9VhT_+i9V9N7NAdCCUgO5xBZpffvVPeh=jK8weZr3WzZ4Bw@mail.gmail.com>

Hi Paul,

I'll post a v2 shortly but will address your comments here.

> >  include/linux/lsm_hooks.h     |  7 +++++++
> >  include/linux/security.h      |  5 +++++
> >  net/vmw_vsock/af_vsock.c      |  1 +
> >  security/security.c           |  5 +++++
> >  security/selinux/hooks.c      | 10 ++++++++++
> >  6 files changed, 29 insertions(+)
> 
> Additional comments below, but I think it would be a good idea for you
> to test your patches on a more traditional Linux distribution as well
> as Android.
> 

No problem, I was going to add a test case into selinux-testsuite
anyway. Done now (link in v2) and tested on Fedora 33 with v5.12-rc3.

> > diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> > index 5546710d8ac1..a9bf3b90cb2f 100644
> > --- a/net/vmw_vsock/af_vsock.c
> > +++ b/net/vmw_vsock/af_vsock.c
> > @@ -755,6 +755,7 @@ static struct sock *__vsock_create(struct net *net,
> >                 vsk->buffer_size = psk->buffer_size;
> >                 vsk->buffer_min_size = psk->buffer_min_size;
> >                 vsk->buffer_max_size = psk->buffer_max_size;
> > +               security_vsock_sk_clone(parent, sk);
> 
> Did you try calling the existing security_sk_clone() hook here?  I
> would be curious to hear why it doesn't work in this case.
> 
> Feel free to educate me on AF_VSOCK, it's entirely possible I'm
> misunderstanding something here :)
> 

No, you're completely right. security_sk_clone does what's needed here.
Adding a new hook was me trying to mimic other socket families going via
selinux_conn_sid. Happy to reuse the existing hook - makes this a nice
oneliner. :)

Please note that I'm marking v2 with 'Fixes' for backporting. This does
feel to me like a bug, an integration that was never considered. Please
shout if you disagree.

-David