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Date:   Mon, 25 Mar 2019 16:42:21 -0700
From:   Stephen Hemminger <stephen@networkplumber.org>
To:     Matthew Garrett <matthewgarrett@google.com>
Cc:     jmorris@namei.org, linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org, dhowells@redhat.com,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        netdev@vger.kernel.org, Chun-Yi Lee <jlee@suse.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Kees Cook <keescook@chromium.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Will Drewry <wad@chromium.org>
Subject: Re: [PATCH 23/27] bpf: Restrict kernel image access functions when
 the kernel is locked down
Message-ID: <20190325164221.5d8687bd@shemminger-XPS-13-9360>
In-Reply-To: <20190325220954.29054-24-matthewgarrett@google.com>
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        <20190325220954.29054-24-matthewgarrett@google.com>
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On Mon, 25 Mar 2019 15:09:50 -0700
Matthew Garrett <matthewgarrett@google.com> wrote:

> From: David Howells <dhowells@redhat.com>
> 
> There are some bpf functions can be used to read kernel memory:
> bpf_probe_read, bpf_probe_write_user and bpf_trace_printk.  These allow
> private keys in kernel memory (e.g. the hibernation image signing key) to
> be read by an eBPF program and kernel memory to be altered without
> restriction.
> 
> Completely prohibit the use of BPF when the kernel is locked down.
> 
> Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: netdev@vger.kernel.org
> cc: Chun-Yi Lee <jlee@suse.com>
> cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Signed-off-by: Matthew Garrett <matthewgarrett@google.com>

Wouldn't this mean that Seccomp won't work in locked down mode?