linux-hardening - Re: [PATCH v4 1/2] powerpc/mm: Support execute-only memory on the Radix MMU

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Date:   Wed, 8 Mar 2023 16:27:02 +0100
From:   Michal Suchánek <msuchanek@...e.de>
To:     Michael Ellerman <patch-notifications@...erman.id.au>
Cc:     linuxppc-dev@...ts.ozlabs.org, Russell Currey <ruscur@...sell.cc>,
        ajd@...ux.ibm.com, anshuman.khandual@....com, npiggin@...il.com,
        linux-hardening@...r.kernel.org, aneesh.kumar@...ux.ibm.com,
        nicholas@...ux.ibm.com
Subject: Re: [PATCH v4 1/2] powerpc/mm: Support execute-only memory on the
 Radix MMU

Hello,

On Wed, Aug 31, 2022 at 11:13:59PM +1000, Michael Ellerman wrote:
> On Wed, 17 Aug 2022 15:06:39 +1000, Russell Currey wrote:
> > Add support for execute-only memory (XOM) for the Radix MMU by using an
> > execute-only mapping, as opposed to the RX mapping used by powerpc's
> > other MMUs.
> > 
> > The Hash MMU already supports XOM through the execute-only pkey,
> > which is a separate mechanism shared with x86.  A PROT_EXEC-only mapping
> > will map to RX, and then the pkey will be applied on top of it.
> > 
> > [...]
> 
> Applied to powerpc/next.
> 
> [1/2] powerpc/mm: Support execute-only memory on the Radix MMU
>       https://git.kernel.org/powerpc/c/395cac7752b905318ae454a8b859d4c190485510

This breaks libaio tests (on POWER9 hash PowerVM):
https://pagure.io/libaio/blob/master/f/harness/cases/5.t#_43

cases/5.p
expect   512: (w), res =   512 [Success]
expect   512: (r), res =   512 [Success]
expect   512: (r), res =   512 [Success]
expect   512: (w), res =   512 [Success]
expect   512: (w), res =   512 [Success]
expect   -14: (r), res =   -14 [Bad address]
expect   512: (r), res =   512 [Success]
expect   512: (w), res =   512 [Success]
test cases/5.t completed PASSED.

cases/5.p
expect   512: (w), res =   512 [Success]
expect   512: (r), res =   512 [Success]
expect   512: (r), res =   512 [Success]
expect   512: (w), res =   512 [Success]
expect   512: (w), res =   512 [Success]
expect   -14: (r), res =   -14 [Bad address]
expect   512: (r), res =   512 [Success]
expect   -14: (w), res =   512 [Success] -- FAILED
test cases/5.t completed FAILED.

Can you have a look if that test assumption is OK?

Thanks

Michal