Tracing unsigned modules

The original discussion didn't really quite capture it all, I think there really are two aspects to this.

The first is that it's quite odd that a (seemingly valid) kernel configuration can result in every single module that you load being loaded as though it was forced, which is what the kernel does before the patch. I'm not sure why this part should be controversial since it just adds more detailed information ("tainted because of missing signature") up front.

The second aspect is about the tracing policy, which says that tracing is disabled for code that's tainted in certain ways (most ways, really, except a few). Since we start from the premise that unsigned modules aren't all that bad (otherwise we could just refuse loading them alltogether, or disallow the configuration that results in this), then to me at least it is strange to argue that tracing should be disabled for such modules.

The whole out-of-tree modules thing is actually a bit of a strawman, because the same happens for in-tree modules, but it's a case where it's even easier to end up with unsigned modules, and it's certainly not an uncommon thing to do (particularly with backports, which is something that some of us have to routinely support).

Now with the second aspect the other question is why tracing is disabled for certain taints to start with - after all we could argue that if the tracing code crashes for you when you have a tainted kernel then you're on your own. As I understand it Steven did this to not even run into the crashing situations (since tracing accesses the ringbuffer in low-level ways), but I would agree that you could argue for an override for allowing that to be overridden.

I tend to think that those aspects are quite unrelated though, and the bulk of the patch is really about the first aspect ("unsigned != forced") even if the reason for it was related to tracing.

exactly, by forcing the module, the admin is saying that they know better than the kernel that this really is what they want to do (and sometimes they may even be right :-) so we should continue to feed the admin rope when they demand it, which is a pretty standard option in the kernel.

> Hmm, you do have a point. We could just make it so that the only taint that fails to load tracepoints is the TAINT_PROPRIETARY_MODULE. And that one fails because of political reasons, not technical ones*.

I'm not sure why we even need that?

What is it that we are trying to prevent by blocking tracing?

If we are trying to prevent crashing, we're already past that point.

If we are trying to make life harder for users of proprietary modules, I don't think there is really agreement on this.