[PATCH] x86, powerpc : pkey-mprotect must allow pkey-0

Ram Pai linuxram at us.ibm.com
Sat Mar 10 16:55:44 AEDT 2018

On Fri, Mar 09, 2018 at 02:40:32PM -0800, Dave Hansen wrote:
> On 03/09/2018 12:12 AM, Ram Pai wrote:
> > Once an address range is associated with an allocated pkey, it cannot be
> > reverted back to key-0. There is no valid reason for the above behavior.  On
> > the contrary applications need the ability to do so.
> Why don't we just set pkey 0 to be allocated in the allocation bitmap by
> default?

ok. that will make it allocatable. But it will not be associatable,
given the bug in the current code. And what will be the
default key associated with a pte? zero? or something else?

> We *could* also just not let it be special and let it be freed.  An app
> could theoretically be careful and make sure nothing is using it.

unable to see how this solves the problem. Need some more explaination.


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