linux-kernel - Re: [PATCH V10 14/44] mm/pkeys: Introduce pks_set

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Date:   Tue, 10 May 2022 22:26:43 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "keescook@...omium.org" <keescook@...omium.org>,
        "Weiny, Ira" <ira.weiny@...el.com>
CC:     "hpa@...or.com" <hpa@...or.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>
Subject: Re: [PATCH V10 14/44] mm/pkeys: Introduce pks_set_readwrite()

On Tue, 2022-05-10 at 15:08 -0700, Kees Cook wrote:
> > Kees would you prefer pks_set_nowrite() as a name?
> 
> I think nowrite is the better name (in the sense that "read-only" can
> sometimes imply non-executable).

I agree with this here. Read-only is a bad name for not writable.
Especially if you try talking about "execute-only" memory which is
"read-only" (not writable) and "not readable". Very confusing.

> 
> > > 
> > > With these changes it should be possible to protect the kernel's
> > > page
> > > table entries from "stray" writes. :)
> > 
> > Yes, Rick has done some great work in that area.
> 
> Oh! I would _love_ to see this series. I was trying to scope the work
> yesterday but gave up after I couldn't figure out the qemu PKS trick.
> :)

I would still like to get back to it, but other work has bumped it for
now.

v1: 
https://lore.kernel.org/lkml/20210505003032.489164-1-rick.p.edgecombe@intel.com/#r

v2: 
https://lore.kernel.org/lkml/20210830235927.6443-1-rick.p.edgecombe@intel.com/#r

Mostly it fit together pretty easily, but there was memory overhead
required to protect the page tables that map the direct map fully
(unless a better solution can be found).