linux-kernel - Re: [PATCH V2 05/10] x86/pks: Add PKS kernel API

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Date:   Tue, 3 Nov 2020 10:42:18 -0800
From:   Ira Weiny <ira.weiny@...el.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>, x86@...nel.org,
        Dan Williams <dan.j.williams@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH V2 05/10] x86/pks: Add PKS kernel API

On Tue, Nov 03, 2020 at 07:14:07PM +0100, Greg KH wrote:
> On Tue, Nov 03, 2020 at 09:53:36AM -0800, Ira Weiny wrote:
> > On Tue, Nov 03, 2020 at 07:50:24AM +0100, Greg KH wrote:
> > > On Mon, Nov 02, 2020 at 12:53:15PM -0800, ira.weiny@...el.com wrote:
> > > > From: Fenghua Yu <fenghua.yu@...el.com>
> > > > 
> > 
> > [snip]
> > 
> > > > diff --git a/include/linux/pkeys.h b/include/linux/pkeys.h
> > > > index 2955ba976048..0959a4c0ca64 100644
> > > > --- a/include/linux/pkeys.h
> > > > +++ b/include/linux/pkeys.h
> > > > @@ -50,4 +50,28 @@ static inline void copy_init_pkru_to_fpregs(void)
> > > >  
> > > >  #endif /* ! CONFIG_ARCH_HAS_PKEYS */
> > > >  
> > > > +#define PKS_FLAG_EXCLUSIVE 0x00
> > > > +
> > > > +#ifndef CONFIG_ARCH_HAS_SUPERVISOR_PKEYS
> > > > +static inline int pks_key_alloc(const char * const pkey_user, int flags)
> > > > +{
> > > > +	return -EOPNOTSUPP;
> > > > +}
> > > > +static inline void pks_key_free(int pkey)
> > > > +{
> > > > +}
> > > > +static inline void pks_mk_noaccess(int pkey)
> > > > +{
> > > > +	WARN_ON_ONCE(1);
> > > 
> > > So for panic-on-warn systems, this is ok to reboot the box?
> > 
> > I would not expect this to reboot the box no.  But it is a violation of the API
> > contract.  If pky_key_alloc() returns an error calling any of the other
> > functions is an error.
> > 
> > > 
> > > Are you sure, that feels odd...
> > 
> > It does feel odd and downright wrong...  But there are a lot of WARN_ON_ONCE's
> > out there to catch this type of internal programming error.  Is panic-on-warn
> > commonly used?
> 
> Yes it is, and we are trying to recover from that as it is something
> that you should recover from.  Properly handle the error and move on.

Sorry, I did not know that...  Ok I'll look at the series because I probably
have others I need to change.

Thanks,
Ira