In addition to IBRS (and microcode support), IBPB
must be used to mitigate variant 2, if retpoline
support is not available. The vulnerability status
of a system will be defined as "non vulnerable"
if IBRS and IBPB are both enabled, or if IBPB
is enabled with a value of 2 for RedHat kernels,
see https://access.redhat.com/articles/3311301
In offline mode, in the worst case where an invalid
config file is given, and we have no vmlinux image
nor System.map, the script was reporting Variant 2
and Variant 3 as vulnerable in the global status.
Replace this by a proper pair of UNKNOWNs
To avoid false negatives when looking for a message
in dmesg, we were previously also grepping in known
on-disk archives of dmesg (dmesg.log, kern.log).
This in turn caused false positives because we have no
guarantee that we're grepping the dmesg of the current
running kernel. Hence we now only look in the live
`dmesg`, detect if it has been truncated, and report
it to the user.
* Add special CoreOS compatibility mode
* CoreOS: refuse --coreos if we're not under CoreOS
* CoreOS: warn if launched without --coreos option
* is_coreos: make stderr silent
* CoreOS: tiny adjustments
* correct is_cpu_vulnerable() comment
As far as I can tell, the function and usage are correct for the comment
to be inverted.
Add a clarifying note as to why the value choice makes sense.
* exit on invalid varient
If this happens, it's a bug in the script. None of the calling code
checks for status 255, so don't let a scripting bug cause a false
negative.
* no need to set vulnerable CPUs
According to comment above this code:
'by default, everything is vulnerable, we work in a "whitelist" logic here.'
We were saying unknown instead of vulnerable when the count of lfence opcodes was low
This was not impacting batch mode or the final decision, just the human-readable output of the script.
