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Date: Wed, 18 Oct 2017 14:29:24 -0700
From: Ram Pai <linuxram@us.ibm.com>
To: Balbir Singh <bsingharora@gmail.com>
Cc: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org,
 benh@kernel.crashing.org, paulus@samba.org,
 khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com,
 hbabu@us.ibm.com, mhocko@kernel.org, bauerman@linux.vnet.ibm.com,
 ebiederm@xmission.com
Subject: Re: [PATCH 18/25] powerpc: check key protection for user page access
Reply-To: Ram Pai <linuxram@us.ibm.com>
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On Thu, Oct 19, 2017 at 06:57:32AM +1100, Balbir Singh wrote:
> On Fri,  8 Sep 2017 15:45:06 -0700
> Ram Pai <linuxram@us.ibm.com> wrote:
> 
> > Make sure that the kernel does not access user pages without
> > checking their key-protection.
> >
> 
> Why? This makes the routines AMR/thread specific? Looks like
> x86 does this as well

Yes. the memkey semantics implemented by x86, assumes that the keys and
their access-permission are per thread.  In other words, a key which is
enabled in the context of one thread, will not be enabled in the context
of another thread.

> but these routines are used by GUP from
> the kernel.

See a problem?

RP