Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH 2/2] powerpc/rtas: block error injection when locked down | Date | Fri, 23 Sep 2022 17:12:44 +1000 |
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Paul Moore <paul@paul-moore.com> writes: > On Thu, Sep 22, 2022 at 3:38 PM Nathan Lynch <nathanl@linux.ibm.com> wrote: >> >> The error injection facility on pseries VMs allows corruption of >> arbitrary guest memory, potentially enabling a sufficiently privileged >> user to disable lockdown or perform other modifications of the running >> kernel via the rtas syscall. >> >> Block the PAPR error injection facility from being opened or called >> when locked down. >> >> Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> >> --- >> arch/powerpc/kernel/rtas.c | 25 ++++++++++++++++++++++++- >> include/linux/security.h | 1 + >> security/security.c | 1 + >> 3 files changed, 26 insertions(+), 1 deletion(-) > > ... > >> diff --git a/include/linux/security.h b/include/linux/security.h >> index 1ca8dbacd3cc..b5d5138ae66a 100644 >> --- a/include/linux/security.h >> +++ b/include/linux/security.h >> @@ -123,6 +123,7 @@ enum lockdown_reason { >> LOCKDOWN_BPF_WRITE_USER, >> LOCKDOWN_DBG_WRITE_KERNEL, >> LOCKDOWN_DEVICE_TREE, >> + LOCKDOWN_RTAS_ERROR_INJECTION, > > With the understanding that I've never heard of RTAS until now, are > there any other RTAS events that would require a lockdown reason? As > a follow up, is it important to distinguish between different RTAS > lockdown reasons? > > I'm trying to determine if we can just call it LOCKDOWN_RTAS.
Yes I think we should.
Currently it only locks down the error injection calls, not all of RTAS.
But firmware can/will add new RTAS calls in future, so it's always possible something will need to be added to the list of things that need to be blocked during lockdown.
So I think calling it LOCKDOWN_RTAS would be more general and future proof, and can be read to mean "lockdown the parts of RTAS that need to be locked down".
Similarly we have LOCKDOWN_ACPI_TABLES which locks down modification to ACPI data, but doesn't disable ACPI use entirely AIUI.
cheers
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