From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Morris Subject: Re: [PATCH V33 24/30] bpf: Restrict bpf when kernel lockdown is in confidentiality mode Date: Thu, 27 Jun 2019 06:22:47 +1000 (AEST) Message-ID: References: <20190621011941.186255-1-matthewgarrett@google.com> <20190621011941.186255-25-matthewgarrett@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Return-path: In-Reply-To: Sender: netdev-owner@vger.kernel.org To: Andy Lutomirski Cc: Matthew Garrett , linux-security@vger.kernel.org, LKML , Linux API , David Howells , Alexei Starovoitov , Matthew Garrett , Network Development , Chun-Yi Lee , Daniel Borkmann , linux-security-module@vger.kernel.org List-Id: linux-api@vger.kernel.org [Adding the LSM mailing list: missed this patchset initially] On Thu, 20 Jun 2019, Andy Lutomirski wrote: > This patch exemplifies why I don't like this approach: > > > @@ -97,6 +97,7 @@ enum lockdown_reason { > > LOCKDOWN_INTEGRITY_MAX, > > LOCKDOWN_KCORE, > > LOCKDOWN_KPROBES, > > + LOCKDOWN_BPF, > > LOCKDOWN_CONFIDENTIALITY_MAX, > > > --- a/security/lockdown/lockdown.c > > +++ b/security/lockdown/lockdown.c > > @@ -33,6 +33,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { > > [LOCKDOWN_INTEGRITY_MAX] = "integrity", > > [LOCKDOWN_KCORE] = "/proc/kcore access", > > [LOCKDOWN_KPROBES] = "use of kprobes", > > + [LOCKDOWN_BPF] = "use of bpf", > > [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", > > The text here says "use of bpf", but what this patch is *really* doing > is locking down use of BPF to read kernel memory. If the details > change, then every LSM needs to get updated, and we risk breaking user > policies that are based on LSMs that offer excessively fine > granularity. Can you give an example of how the details might change? > I'd be more comfortable if the LSM only got to see "confidentiality" > or "integrity". These are not sufficient for creating a useful policy for the SELinux case. -- James Morris