And we've been avoiding that drivers can self declare auditing, we've been
trying to have a separate centralized list so that it's easier to enforce
and avoids any cut'n'paste mistakes.
-Andi
Now I'm confused. What is proposed here seems to be basically that,
drivers need to declare auditing by replacing ioremap with
ioremap_shared.
Auditing is declared on the device model level using a central allow list.
Can we not have an init call allow list instead of, or in addition to, a
device allow list?
That would be quite complicated and intrusive. In fact I'm not even sure
how to do maintain something like this. There are a lot of needed
initcalls, they would all need to be marked. How can we distinguish
them? It would be a giant auditing project. And of course how would you
prevent it from bitrotting?
Basically it would be hundreds of changes all over the tree, just to
avoid two changes in virtio and MSI. Approach of just stopping the
initcalls from doing bad things is much less intrusive.
But this cannot do anything to initcalls that run before probe,
Can't we extend module_init so init calls are validated against the
allow list?
See above.
Also the problem isn't really with modules (we rely on udev not loading
them), but with builtin initcalls
that's why
an extra level of defense of ioremap opt-in is useful.
OK even assuming this, why is pci_iomap opt-in useful?
That never happens before probe - there's simply no pci_device then.
Hmm, yes that's true. I guess we can make it default to opt-in for
pci_iomap.
It only really matters for device less ioremaps.
It looks suspiciously like drivers self-declaring auditing to me which
we both seem to agree is undesirable. What exactly is the difference?
Just allow listing the ioremaps is not self declaration because the
device will still not initialize due to the central device filter. If
you want to use it that has to be changed.
It's just an additional safety net to contain code running before probe.
Or are you just trying to disable anything that runs before probe?
Well anything that could do dangerous host interactions (like processing
ioremap data) A lot of things are harmless and can be allowed, or
already blocked elsewhere (e.g. we have a IO port filter). This just
handles the ioremap/MMIO case.
In that case I don't see a reason to touch pci drivers though.
These should be fine with just the device model list.
That won't stop initcalls.
-Andi
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