Re: [PATCH 23/27] bpf: Restrict kernel image access functions when the kernel is locked down
From: Jordan Glover <hidden>
Date: 2019-03-26 13:54:51
Also in:
linux-security-module, lkml
On Tuesday, March 26, 2019 12:00 AM, Daniel Borkmann [off-list ref] wrote:
On 03/26/2019 12:42 AM, Stephen Hemminger wrote:quoted
On Mon, 25 Mar 2019 15:09:50 -0700 Matthew Garrett matthewgarrett@google.com wrote:quoted
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.quoted
quoted
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