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From: Kees Cook <keescook@chromium.org>
To: KP Singh <kpsingh@chromium.org>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>,
	Casey Schaufler <casey@schaufler-ca.com>,
	linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
	LSM List <linux-security-module@vger.kernel.org>,
	Brendan Jackman <jackmanb@google.com>,
	Florent Revest <revest@google.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	James Morris <jmorris@namei.org>, Paul Turner <pjt@google.com>,
	Jann Horn <jannh@google.com>,
	Florent Revest <revest@chromium.org>,
	Brendan Jackman <jackmanb@chromium.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Paul Moore <paul@paul-moore.com>
Subject: Re: [PATCH bpf-next v5 4/7] bpf: lsm: Implement attach, detach and execution
Date: Tue, 24 Mar 2020 11:34:52 -0700
Message-ID: <202003241133.16C02BE5B@keescook> (raw)
In-Reply-To: <20200324183130.GA6784@chromium.org>

On Tue, Mar 24, 2020 at 07:31:30PM +0100, KP Singh wrote:
> On 24-Mär 19:27, KP Singh wrote:
> > We do not have a specific capable check for BPF_PROG_TYPE_LSM programs
> > now. There is a general check which requires CAP_SYS_ADMIN when
> > unprivileged BPF is disabled:
> > 
> > in kernel/bpf/sycall.c:
> > 
> >         if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN))
> > 	        return -EPERM;
> > 
> > AFAIK, Most distros disable unprivileged eBPF.
> > 
> > Now that I look at this, I think we might need a CAP_MAC_ADMIN check
> > though as unprivileged BPF being enabled will result in an
> > unprivileged user being able to load MAC policies.
> 
> Actually we do have an extra check for loading BPF programs:
> 
> 
> in kernel/bpf/syscall.c:bpf_prog_load
> 
> 	if (type != BPF_PROG_TYPE_SOCKET_FILTER &&
> 	    type != BPF_PROG_TYPE_CGROUP_SKB &&
> 	    !capable(CAP_SYS_ADMIN))
> 		return -EPERM;
> 
> Do you think we still need a CAP_MAC_ADMIN check for LSM programs?

IMO, these are distinct privileges on the non-SELinux system. I think
your patch is fine as-is.

-- 
Kees Cook

  reply index

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-23 16:44 [PATCH bpf-next v5 0/8] MAC and Audit policy using eBPF (KRSI) KP Singh
2020-03-23 16:44 ` [PATCH bpf-next v5 1/7] bpf: Introduce BPF_PROG_TYPE_LSM KP Singh
2020-03-23 19:02   ` Yonghong Song
2020-03-23 16:44 ` [PATCH bpf-next v5 2/7] security: Refactor declaration of LSM hooks KP Singh
2020-03-23 19:33   ` Kees Cook
2020-03-23 19:56   ` Andrii Nakryiko
2020-03-24 16:06     ` KP Singh
2020-03-23 16:44 ` [PATCH bpf-next v5 3/7] bpf: lsm: provide attachment points for BPF LSM programs KP Singh
2020-03-23 19:04   ` Yonghong Song
2020-03-23 19:33   ` Kees Cook
2020-03-23 19:59   ` Andrii Nakryiko
2020-03-24 10:39     ` KP Singh
2020-03-24 16:12       ` KP Singh
2020-03-24 21:26         ` Andrii Nakryiko
2020-03-24 22:39           ` KP Singh
2020-03-23 16:44 ` [PATCH bpf-next v5 4/7] bpf: lsm: Implement attach, detach and execution KP Singh
2020-03-23 19:16   ` Yonghong Song
2020-03-23 19:44     ` KP Singh
2020-03-23 20:18   ` Andrii Nakryiko
2020-03-24 19:00     ` KP Singh
2020-03-24 14:35   ` Stephen Smalley
2020-03-24 14:50     ` KP Singh
2020-03-24 14:58       ` Stephen Smalley
2020-03-24 16:25         ` Casey Schaufler
2020-03-24 17:49           ` Stephen Smalley
2020-03-24 18:01             ` Kees Cook
2020-03-24 18:06               ` KP Singh
2020-03-24 18:21                 ` Stephen Smalley
2020-03-24 18:27                   ` KP Singh
2020-03-24 18:31                     ` KP Singh
2020-03-24 18:34                       ` Kees Cook [this message]
2020-03-24 18:33                   ` Kees Cook
2020-03-23 16:44 ` [PATCH bpf-next v5 5/7] bpf: lsm: Initialize the BPF LSM hooks KP Singh
2020-03-23 19:44   ` Kees Cook
2020-03-23 19:47     ` KP Singh
2020-03-23 20:21       ` Andrii Nakryiko
2020-03-23 20:47     ` Casey Schaufler
2020-03-23 21:44       ` Kees Cook
2020-03-24  1:13   ` Casey Schaufler
2020-03-24  1:52     ` KP Singh
2020-03-24 14:37       ` Stephen Smalley
2020-03-24 14:42         ` KP Singh
2020-03-24 14:51           ` Stephen Smalley
2020-03-24 14:51             ` KP Singh
2020-03-24 17:57               ` Kees Cook
2020-03-23 16:44 ` [PATCH bpf-next v5 6/7] tools/libbpf: Add support for BPF_PROG_TYPE_LSM KP Singh
2020-03-23 19:21   ` Yonghong Song
2020-03-23 20:25   ` Andrii Nakryiko
2020-03-24  1:57     ` KP Singh
2020-03-23 16:44 ` [PATCH bpf-next v5 7/7] bpf: lsm: Add selftests " KP Singh
2020-03-23 20:04   ` Yonghong Song
2020-03-24 20:04     ` KP Singh
2020-03-24 23:54   ` Andrii Nakryiko
2020-03-25  0:36     ` KP Singh

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