linux-kernel - Re: [PATCH v4 16/24] powerpc/pseries: Implement signed update for PLPKS objects

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Message-ID: <658d61ef8b6b6bb45fa946283b04c75dfac7a749.camel@russell.cc>
Date:   Tue, 31 Jan 2023 15:23:52 +1100
From:   Russell Currey <ruscur@...sell.cc>
To:     Andrew Donnellan <ajd@...ux.ibm.com>,
        Nicholas Piggin <npiggin@...il.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-integrity@...r.kernel.org
Cc:     sudhakar@...ux.ibm.com, bgray@...ux.ibm.com, erichte@...ux.ibm.com,
        gregkh@...uxfoundation.org, nayna@...ux.ibm.com,
        linux-kernel@...r.kernel.org, zohar@...ux.ibm.com,
        gjoyce@...ux.ibm.com, gcwilson@...ux.ibm.com, joel@....id.au
Subject: Re: [PATCH v4 16/24] powerpc/pseries: Implement signed update for
 PLPKS objects

On Mon, 2023-01-30 at 15:43 +1100, Andrew Donnellan wrote:
> On Tue, 2023-01-24 at 14:16 +1000, Nicholas Piggin wrote:
> > > diff --git a/arch/powerpc/platforms/pseries/plpks.c
> > > b/arch/powerpc/platforms/pseries/plpks.c
> > > index 1189246b03dc..796ed5544ee5 100644
> > > --- a/arch/powerpc/platforms/pseries/plpks.c
> > > +++ b/arch/powerpc/platforms/pseries/plpks.c
> > > @@ -81,6 +81,12 @@ static int pseries_status_to_err(int rc)
> > >                 err = -ENOENT;
> > >                 break;
> > >         case H_BUSY:
> > > +       case H_LONG_BUSY_ORDER_1_MSEC:
> > > +       case H_LONG_BUSY_ORDER_10_MSEC:
> > > +       case H_LONG_BUSY_ORDER_100_MSEC:
> > > +       case H_LONG_BUSY_ORDER_1_SEC:
> > > +       case H_LONG_BUSY_ORDER_10_SEC:
> > > +       case H_LONG_BUSY_ORDER_100_SEC:
> > >                 err = -EBUSY;
> > >                 break;
> > >         case H_AUTHORITY:
> > 
> > This is a bit sad to maintain here. It's duplicating bits with
> > hvcs_convert, and a bunch of open coded places. Probably not the
> > series to do anything about. Would be nice if we could standardise
> > it though.
> 
> Agreed - though we're not going to touch it in this series.
> 
> > 
> > > @@ -184,14 +190,17 @@ static struct label *construct_label(char
> > > *component, u8 varos, u8 *name,
> > >                                      u16 namelen)
> > >  {
> > >         struct label *label;
> > > -       size_t slen;
> > > +       size_t slen = 0;
> > >  
> > >         if (!name || namelen > PLPKS_MAX_NAME_SIZE)
> > >                 return ERR_PTR(-EINVAL);
> > >  
> > > -       slen = strlen(component);
> > > -       if (component && slen > sizeof(label->attr.prefix))
> > > -               return ERR_PTR(-EINVAL);
> > > +       // Support NULL component for signed updates
> > > +       if (component) {
> > > +               slen = strlen(component);
> > > +               if (slen > sizeof(label->attr.prefix))
> > > +                       return ERR_PTR(-EINVAL);
> > > +       }
> > 
> > Is this already a bug? Code checks for component != NULL but
> > previously
> > calls strlen which would oops on NULL component AFAIKS. Granted
> > nothing
> > is actually using any of this these days.
> 
> True, it should have been checking for NULL first, but as you say no-
> one is using it.
> 
> > 
> > It already seems like it's supposed to be allowed to rad NULL
> > component
> > with read_var though? Why the differences, why not always allow
> > NULL
> > component? (I assume there is some reason, I just don't know
> > anything
> > about secvar or secure boot).
> 
> I think the comment confuses more than it clarifies, I'll remove it.
> 
> As you say, read_var() should work fine with component == NULL,
> though
> write_var() checks it. The only rule I can find in the spec is that
> signed update calls *must* set the component to NULL. I'm seeking
> clarification on that.

Signed update calls *must* set the component to NULL.

We could just call construct_label() with NULL as the component
directly but I think it's better to explicitly check var->component and
return so the caller knows what they're trying to do is wrong.

> 
> > > +EXPORT_SYMBOL(plpks_signed_update_var);
> > 
> > Sorry I missed it before -- can this be a _GPL export?
> 
> Indeed it should be - actually, I should check if I can get rid of
> the
> export completely...
>