[PATCH 18/25] powerpc: check key protection for user page access

[Ram Pai]

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 at 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