** Changed in: ubuntu-power-systems
Status: Fix Committed => Fix Released
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https://bugs.launchpad.net/bugs/1863562
Title:
Restrict xmon to read-only-mode if kernel is locked down
Status in The Ubuntu-power-systems project:
Fix Released
Status in linux package in Ubuntu:
Fix Released
Bug description:
This is a spin off of LP 1855668 (see comment #11 there:)
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
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