On 06/08/2018 12:15 PM, Michal Suchánek wrote:
On Fri, 8 Jun 2018 07:53:51 +0200
Florian Weimer <fweimer@xxxxxxxxxx> wrote:
On 06/08/2018 04:34 AM, Ram Pai wrote:
So the remaining question at this point is whether the Intel
behavior (default-deny instead of default-allow) is preferable.
Florian, remind me what behavior needs to fixed?
See the other thread. The Intel register equivalent to the AMR by
default disallows access to yet-unallocated keys, so that threads
which are created before key allocation do not magically gain access
to a key allocated by another thread.
That does not make any sense. The threads share the address space so
they should also share the keys.
Or in other words the keys are supposed to be acceleration of
mprotect() so if mprotect() magically gives access to threads that did
not call it so should pkey functions. If they cannot do that then they
fail the primary purpose.
That's not how protection keys work. The access rights are
thread-specific, so that you can change them locally, without
synchronization and expensive inter-node communication.
Thanks,
Florian
