Comment 11 for bug 1855668

------- Comment From <email address hidden> 2020-02-17 00:27 EDT-------
Hi,

I'm sorry, I thought I had already mentioned this but it was a case of me getting projects and teams mixed up.

Please could you pick up (in addition to the issue still pending) commit
69393cb03ccd ("powerpc/xmon: Restrict when kernel is locked down").

From the pull-request that included it, the commit does the following:

- A change to xmon (our crash handler / pseudo-debugger) to restrict
it to read-only mode when the kernel is lockdown'ed, otherwise it's
trivial to drop into xmon and modify kernel data, such as the
lockdown state.

To exploit this you'd need to boot with command line including 'xmon=rw', as xmon isn't read-write by default on the Focal kernel, but that's not exactly a challenge. I have used this to drop down from lockdown=confidentiality to lockdown=none on 5.4.0-14-generic #17-Ubuntu

Regards,
Daniel