linux-kernel - Re: [PATCH, RFC 45/62] mm: Add the encrypt

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Date:   Fri, 14 Jun 2019 17:32:31 -0700
From:   Alison Schofield <alison.schofield@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...capital.net>,
        David Howells <dhowells@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>, linux-mm@...ck.org,
        kvm@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH, RFC 45/62] mm: Add the encrypt_mprotect() system call
 for MKTME

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:
> > + *	(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?