Messages in this thread | | | Subject | Re: [PATCH] x86, powerpc : pkey-mprotect must allow pkey-0 | From | Florian Weimer <> | Date | Wed, 14 Mar 2018 09:00:36 +0100 |
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On 03/09/2018 09:00 PM, Ram Pai wrote: > On Fri, Mar 09, 2018 at 12:04:49PM +0100, Florian Weimer wrote: >> On 03/09/2018 09:12 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. >> >> mprotect without a key does not necessarily use key 0, e.g. if >> protection keys are used to emulate page protection flag combination >> which is not directly supported by the hardware. >> >> Therefore, it seems to me that filtering out non-allocated keys is >> the right thing to do. > > I am not sure, what you mean. Do you agree with the patch or otherwise?
I think it's inconsistent to make key 0 allocated, but not the key which is used for PROT_EXEC emulation, which is still reserved. Even if you change the key 0 behavior, it is still not possible to emulate mprotect behavior faithfully with an allocated key.
Thanks, Florian
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