From: Ram Pai <linuxram@us.ibm.com>
To: "Michal Suchánek" <msuchanek@suse.de>
Cc: Dave Hansen <dave.hansen@intel.com>,
fweimer@redhat.com, Ingo Molnar <mingo@kernel.org>,
mhocko@kernel.org, Ulrich.Weigand@de.ibm.com, paulus@samba.org,
aneesh.kumar@linux.vnet.ibm.com, bauerman@linux.vnet.ibm.com,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v3] powerpc, pkey: make protection key 0 less special
Date: Sun, 6 May 2018 13:10:43 -0700 [thread overview]
Message-ID: <20180506201043.GE5617@ram.oc3035372033.ibm.com> (raw)
In-Reply-To: <20180505143956.139f4828@naga.suse.cz>
On Sat, May 05, 2018 at 02:39:56PM +0200, Michal Suchánek wrote:
> On Fri, 4 May 2018 14:45:07 -0700
> Ram Pai <linuxram@us.ibm.com> wrote:
>
> > On Fri, May 04, 2018 at 02:31:10PM -0700, Dave Hansen wrote:
> > > On 05/04/2018 02:26 PM, Michal Suchánek wrote:
> > > > If it is not ok to change permissions of pkey 0 is it ok to free
> > > > it?
> > >
> > > It's pretty much never OK to free it on x86 or ppc. But, we're not
> > > going to put code in to keep userspace from shooting itself in the
> > > foot, at least on x86.
> >
> > and on powerpc aswell.
>
> But once it's free it can be re-allocated. So you are moving the
> special-casing from free code to code dealing with allocation.
Actually if an application frees key-0, it has potentially opened up a
can-of-worms. It could step on anything that explodes.
Its choice between imposing policies on an application v/s freeing it up
to choose its own policy. I think the kernel should impose some form of
mild-policy. But others think there should be none.
>
> If you want something like allocate_exec_only_pkey then the function
> (either in kernel or in userspace) needs to make sure it is not
> getting/requesting key 0 on powerpc.
Yes. makes sense. I will put in some checks towards that.
Thanks,
RP
>
> Thanks
>
> Michal
--
Ram Pai
next prev parent reply other threads:[~2018-05-06 20:10 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-04 19:22 [PATCH v3] powerpc, pkey: make protection key 0 less special Ram Pai
2018-05-04 19:59 ` Dave Hansen
2018-05-04 20:21 ` Ram Pai
2018-05-04 21:26 ` Michal Suchánek
2018-05-04 21:31 ` Dave Hansen
2018-05-04 21:45 ` Ram Pai
2018-05-05 12:39 ` Michal Suchánek
2018-05-06 20:10 ` Ram Pai [this message]
2018-05-07 11:21 ` Michal Suchánek
2018-05-08 16:38 ` Ram Pai
2018-05-08 17:03 ` Michal Suchánek
2018-05-08 18:38 ` Ram Pai
2018-05-09 15:43 ` Michal Suchánek
2018-05-09 15:46 ` Dave Hansen
2018-05-09 15:56 ` Michal Suchánek
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