Alan Cox wrote:
It would be nice not to export it at all or to protect it, paravirt_ops
is a rootkit authors dream ticket. I'm opposed to paravirt_ops until it
is properly protected, its an unpleasantly large security target if not.
Do you have an example of an attack which would become significantly
easier with pv_ops in use? I agree it might make a juicy target, but
surely it is just a matter of degree given that any attacker who can get
to pv_ops can do pretty much anything else.
It would be a lot safer if we could have the struct paravirt_ops in
protected read-only const memory space, set it up in the core kernel
early on in boot when we play "guess todays hypervisor" and then make
sure it stays in read only (even to kernel) space.
Yes, I'd thought about doing something like that, but as Arjan pointed
out, nothing is actually read-only in the kernel when using a 2M
mapping. It's also ameliorated by the fact that some of the entrypoints
are never used at runtime, because the code has been patched inline (but
I don't think it would ever be desirable to patch every entrypoint,
since some are just not worth the effort, complexity or obfuscation
which result from patching).
J
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