linux-kernel - Re: [PATCH v12 04/10] KEYS: Move KEY_LOOKUP

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Date:   Fri, 26 Aug 2022 09:14:09 +0200
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...ux.dev, song@...nel.org, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, mykolal@...com,
        corbet@....net, dhowells@...hat.com, rostedt@...dmis.org,
        mingo@...hat.com, paul@...l-moore.com, jmorris@...ei.org,
        serge@...lyn.com, shuah@...nel.org, bpf@...r.kernel.org,
        linux-doc@...r.kernel.org, keyrings@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        deso@...teo.net, Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH v12 04/10] KEYS: Move KEY_LOOKUP_ to include/linux/key.h

On Fri, 2022-08-26 at 08:42 +0300, Jarkko Sakkinen wrote:
> On Thu, Aug 18, 2022 at 05:29:23PM +0200, 
> roberto.sassu@...weicloud.com wrote:
> > From: Roberto Sassu <roberto.sassu@...wei.com>
> > 
> > In preparation for the patch that introduces the
> > bpf_lookup_user_key() eBPF
> > kfunc, move KEY_LOOKUP_ definitions to include/linux/key.h, to be
> > able to
> > validate the kfunc parameters.
> > 
> > Also, introduce key_lookup_flags_check() directly in
> > include/linux/key.h,
> > to reduce the risk that the check is not in sync with currently
> > defined
> > flags.
> 
> Missing the description what the heck this function even is.
> 
> Please, explain that.

Hi Jarkko

sorry, forgot to update the commit description. Will do it.

> Also, the short subject is misleading because this *just*
> does not move flags.
> 
> > Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> > Reviewed-by: KP Singh <kpsingh@...nel.org>
> > ---
> >  include/linux/key.h      | 11 +++++++++++
> >  security/keys/internal.h |  2 --
> >  2 files changed, 11 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/linux/key.h b/include/linux/key.h
> > index 7febc4881363..b5bbae77a9e7 100644
> > --- a/include/linux/key.h
> > +++ b/include/linux/key.h
> > @@ -88,6 +88,17 @@ enum key_need_perm {
> >  	KEY_DEFER_PERM_CHECK,	/* Special: permission check is
> > deferred */
> >  };
> >  
> > +#define KEY_LOOKUP_CREATE	0x01
> > +#define KEY_LOOKUP_PARTIAL	0x02
> > +
> 
> /*
>  * Explain what the heck this function is.
>  */
> > +static inline int key_lookup_flags_check(u64 flags)
> > +{
> > +	if (flags & ~(KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL))
> > +		return -EINVAL;
> > +
> > +	return 0;
> > +}
> 
> This is essentially a boolean function, right?
> 
> I.e. the implementation can be just:
> 
> !!(flags & ~(KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL))

Absolutely fine with that, if you prefer.

> Not even sure if this is needed in the first place, or
> would it be better just to open code it. How many call
> sites does it have anyway?
> 

Daniel preferred to have this check here.

Thanks

Roberto