Re: [PATCH 4/4] x86,module: Detect CRn and DRn manipulation

[Peter Zijlstra]

On Wed, Apr 08, 2020 at 09:27:26AM -0400, Steven Rostedt wrote:
> On Tue, 07 Apr 2020 13:02:40 +0200
> Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> > +		if (insn_is_mov_CRn(&insn) || insn_is_mov_DRn(&insn)) {
> > +			pr_err("Module writes to CRn or DRn, please use the proper accessors: %s\n", mod->name);
> > +			return -ENOEXEC;
> > +		}
> > +
> 
> Something like this should be done for all modules, not just out of tree
> modules.

I'm all for it; but people were worried scanning all modules was too
expensive (I don't really believe it is, module loading just can't be a
hot-path). Also, in-tree modules are audited a lot more than out of tree
magic voodoo crap.