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

Peter Zijlstra
2020-04-08T15:44:51Z

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@infradead.org> 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.