On Tue, Apr 3, 2018 at 8:41 AM, Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > On Tue, Apr 03, 2018 at 08:11:07AM -0700, Andy Lutomirski wrote: >> > >> >> "bpf: Restrict kernel image access functions when the kernel is locked down": >> >> This patch just sucks in general. >> > >> > Yes - but that's what Alexei Starovoitov specified. bpf kind of sucks since >> > it gives you unrestricted access to the kernel. >> >> bpf, in certain contexts, gives you unrestricted access to *reading* >> kernel memory. bpf should, under no circumstances, let you write to >> the kernel unless you're using fault injection or similar. >> >> I'm surprised that Alexei acked this patch. If something like XDP or >> bpfilter starts becoming widely used, this patch will require a lot of >> reworking to avoid breaking standard distros. > > my understanding was that this lockdown set attemps to disallow _reads_ > of kernel memory from anything, so first version of patch was adding > run-time checks for bpf_probe_read() which is no-go > and without this helper the bpf for tracing is losing a lot of its power, > so the easiest is to disable it all. Fair enough. > I think lockdown suppose to disable xdp, bpfilter, nflog, raw sockets + pcap too > otherwise even cap_net_admin can see traffic coming into host. > Similarly kprobe, perf_event, ftrace should be off as well? > I'm reasonably sure that lockdown is not intended to be this far reaching. cap_net_admin can see traffic coming into the host, and I don't think lockdown is intended to change that. David, I think this is exactly why you need to define what "lockdown" means. As it stands, the best argument I've seen involves "blacklisting", but that's a political thing and almost no one involved has any ability to evaluate it. Right now there's a series of patches that check for "lockdown" and seem to disable things that make someone uncomfortable. That's not a good way to design a security feature. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
