Messages in this thread | | | From | Matthew Garrett <> | Date | Tue, 20 Feb 2018 20:37:34 +0000 | Subject | Re: [PATCH] Make kernel taint on invalid module signatures configurable |
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On Tue, Feb 20, 2018 at 11:21 AM Jessica Yu <jeyu@kernel.org> wrote:
> Ah, OK. So if I'm understanding correctly, you want to use the same kernel > image/configuration but for two different use cases, one where the module > signatures do not matter, and one where they do matter. But the config you > want to use in both use cases would have CONFIG_MODULE_SIG=y and > CONFIG_MODULE_SIG_TAINT=n (to avoid tainting of unsigned/invalidly signed > modules).
Right. Distributions generally have to try to satisfy multiple use cases with as few kernel images as possible.
> In any case, I think I'd be willing to merge it as a module_param made > available under CONFIG_MODULE_SIG=y (rather than as a new separate config > option), while preserving the default behavior of tainting on > unsigned/invalidly signed module loads (so let's keep the param parts of > your patch). I think it makes sense to consider the turning-off-the-taint > param as a behavioral tweak under CONFIG_MODULE_SIG. Then you could turn > off the tainting behavior on the kernel command line, would this sufficient > enough for your use cases?
I think that's probably not practical - distributions often aren't in control of the kernel command line after initial installation, so they'd end up with different behaviour depending on whether a machine was a clean install or not (which is why several things that are module_params have defaults controlled by additional kernel config options)
> >Not entirely. There's two cases where the current situation causes problems: > > > >1) Distributions that build out of tree kernel modules and don't have > >infrastructure to sign them will end up with kernel taint. That's something > >that can be resolved by implementing that infrastructure. > >2) End-users who build out of tree kernel modules will end up with kernel > >taint and will file bugs. This cannot be fixed but will increase > >distribution load anyway.
> I thought these two cases (particularly #2) were the very situations > where distros might find the unsigned module taint useful (especially > in the use case where you do benefit from module signatures). From my > understanding, the unsigned module taint is intended to be useful when > looking at crashes/OOPses, to provide a clear indication of whether or > not a developer could reliably debug the crash, or choose to tread > carefully, because the end-user has loaded an unsigned/out-of-tree > module that wasn't signed/shipped by the distribution. Is the taint > just not useful to distros in this manner anymore?
The module list is usually sufficient for that - users tend not to replace individual distribution modules without rebuilding their entire kernel.
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