Re: [PATCH 22/27] Lock down kprobes

[Matthew Garrett]

On Tue, Mar 26, 2019 at 5:30 AM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
>
> On Mon, 25 Mar 2019 15:09:49 -0700
> Matthew Garrett <matthewgarrett@xxxxxxxxxx> wrote:
>
> > From: David Howells <dhowells@xxxxxxxxxx>
> >
> > Disallow the creation of kprobes when the kernel is locked down by
> > preventing their registration.  This prevents kprobes from being used to
> > access kernel memory, either to make modifications or to steal crypto data.
>
> Hmm, if you enforce signature check of modules, those modules
> should be allowed to use kprobes?
> I think we should introduce some kind of trust inheritance from
> signed (trusted) modules.

Is there any way to install a kprobe /without/ it coming from a
module? The presumption in lockdown mode is that module signing is
enforced, so I'll admit to not being entirely clear on why this patch
is needed in that case.