Re: [PATCH v2 1/7] sysfs/cpu: Add "Unknown" vulnerability state

From: Jeremy Linton
Date: Thu Jan 03 2019 - 11:38:22 EST

On 01/03/2019 03:38 AM, Greg Kroah-Hartman wrote:
On Wed, Jan 02, 2019 at 06:49:15PM -0600, Jeremy Linton wrote:
There is a lot of variation in the Arm ecosystem. Because of this,
there exist possible cases where the kernel cannot authoritatively
determine if a machine is vulnerable.

Really? Why not? What keeps you from "knowing" this? Can't the
developer of the chip tell you?

There tends to be a few cases, possibly incomplete white/black lists, firmware that isn't responding correctly, or the user didn't build in the code to check the mitigation (possibly because its an embedded system and they know its not vulnerable?).

I would hope that it is an exceptional case.

Rather than guess the vulnerability status in cases where
the mitigation is disabled or the firmware isn't responding
correctly, we need to display an "Unknown" state.

Shouldn't "Unknown" really be the same thing as "Vulnerable"? A user
should treat it the same way, "Unknown" makes it feel like "maybe I can
just ignore this and hope I really am safe", which is not a good idea at

I tend to agree its not clear what to do with "unknown".

OTOH, I think there is a hesitation to declare something vulnerable when it isn't. Meltdown for example, is fairly rare given that it currently only affects a few arm parts, so declaring someone vulnerable when they likely aren't is going to be just as difficult to explain.