Messages in this thread | | | Date | Tue, 26 Mar 2019 13:54:40 +0000 | From | Jordan Glover <> | Subject | Re: [PATCH 23/27] bpf: Restrict kernel image access functions when the kernel is locked down |
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On Tuesday, March 26, 2019 12:00 AM, Daniel Borkmann <daniel@iogearbox.net> wrote:
> On 03/26/2019 12:42 AM, Stephen Hemminger wrote: > > > 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. > > I'm not sure where 'kernel memory to be altered without restriction' comes > from, but it's definitely a wrong statement. > > > > Completely prohibit the use of BPF when the kernel is locked down. > > In which scenarios will the lock-down mode be used? Mostly niche? I'm asking > as this would otherwise break a lot of existing stuff ... I'd prefer you find > a better solution to this than this straight -EPERM rejection.
AFAIK this change breaks IPAddressAllow/IPAddressDeny usage in systemd services which makes them LESS secure.
https://www.freedesktop.org/software/systemd/man/systemd.resource-control.html https://github.com/systemd/systemd/blob/04d7ca022843913fba5170c40be07acf2ab5902b/README#L96
Jordan
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