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

On Fri, Mar 09, 2018 at 02:40:32PM -0800, Dave Hansen wrote:

On 03/09/2018 12:12 AM, Ram Pai wrote:

quoted

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.


RP