Re: [PATCH v8 04/12] x86/spectre: Add boot time option to select Spectre v2 mitigation

[Jiri Kosina]

On Wed, 24 Jan 2018, Greg Kroah-Hartman wrote:

> > > I just thought since you were already using modversions in enterprise 
> > > distros already, that adding it there would be the simplest.
> > 
> > The patch as-is introduces immediate modversion mismatch between 
> > retpolined kernel and non-retpolined module, making each and every one 
> > fail to load.
> 
> Good, the patch works then, because I thought that not loading
> non-retpolined modules in a kernel that was built with retpoline was the
> goal here.

No, we do not want to break loading of externally-built modules just 
because they might contain indirect calls.

Warning in such situations / tainting the kernel / reporting "might be 
vulnerable" in sysfs should be the proper way to go.

retpolines are not kernel ABI (towards modules) breaker, so let's not 
pretend it is.

Thanks,

-- 
Jiri Kosina
SUSE Labs