Re: [PATCH, RFC 45/62] mm: Add the encrypt_mprotect() system call for MKTME

[Peter Zijlstra]

On Fri, Jun 14, 2019 at 05:32:31PM -0700, Alison Schofield wrote:
> On Fri, Jun 14, 2019 at 01:51:37PM +0200, Peter Zijlstra wrote:
> > On Wed, May 08, 2019 at 05:44:05PM +0300, Kirill A. Shutemov wrote:
> snip
> > >  /*
> > > - * When pkey==NO_KEY we get legacy mprotect behavior here.
> > > + * do_mprotect_ext() supports the legacy mprotect behavior plus extensions
> > > + * for Protection Keys and Memory Encryption Keys. These extensions are
> > > + * mutually exclusive and the behavior is:

Well, here it states that the extentions are mutually exclusive.

> > > + *	(pkey==NO_KEY && keyid==NO_KEY) ==> legacy mprotect
> > > + *	(pkey is valid)  ==> legacy mprotect plus Protection Key extensions
> > > + *	(keyid is valid) ==> legacy mprotect plus Encryption Key extensions
> > >   */
> > >  static int do_mprotect_ext(unsigned long start, size_t len,
> > > -		unsigned long prot, int pkey)
> > > +			   unsigned long prot, int pkey, int keyid)
> > >  {
> 
> snip
> 
> >
> > I've missed the part where pkey && keyid results in a WARN or error or
> > whatever.
> > 
> I wasn't so sure about that since do_mprotect_ext()
> is the call 'behind' the system calls. 
> 
> legacy mprotect always calls with: NO_KEY, NO_KEY
> pkey_mprotect always calls with:  pkey, NO_KEY
> encrypt_mprotect always calls with  NO_KEY, keyid
> 
> Would a check on those arguments be debug only 
> to future proof this?

But you then don't check that, anywhere, afaict.