linux-hardening - Re: [PATCH] gcc-plugins: Undefine LATENT_ENTROPY

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Date:   Wed, 17 Aug 2022 13:09:33 +1000
From:   Andrew Donnellan <ajd@...ux.ibm.com>
To:     Yury Norov <yury.norov@...il.com>
Cc:     Erhard Furtner <erhard_f@...lbox.org>,
        Emese Revfy <re.emese@...il.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] gcc-plugins: Undefine LATENT_ENTROPY_PLUGIN when plugin
 disabled for a file

On Tue, 2022-08-16 at 05:14 -0700, Yury Norov wrote:
> On Tue, Aug 16, 2022 at 03:17:20PM +1000, Andrew Donnellan wrote:
> > Commit 36d4b36b6959 ("lib/nodemask: inline next_node_in() and
> > node_random()") refactored some code by moving node_random() from
> > lib/nodemask.c to include/linux/nodemask.h, thus requiring
> > nodemask.h to
> > include random.h, which conditionally defines add_latent_entropy()
> > depending on whether the macro LATENT_ENTROPY_PLUGIN is defined.
> > 
> > This broke the build on powerpc, where nodemask.h is indirectly
> > included
> > in arch/powerpc/kernel/prom_init.c, part of the early boot
> > machinery that
> > is excluded from the latent entropy plugin using
> > DISABLE_LATENT_ENTROPY_PLUGIN. It turns out that while we add a gcc
> > flag
> > to disable the actual plugin, we don't undefine
> > LATENT_ENTROPY_PLUGIN.
> > 
> > This leads to the following:
> > 
> >     CC      arch/powerpc/kernel/prom_init.o
> >   In file included from ./include/linux/nodemask.h:97,
> >                    from ./include/linux/mmzone.h:17,
> >                    from ./include/linux/gfp.h:7,
> >                    from ./include/linux/xarray.h:15,
> 
> As a side note, xarray can go with gfp_types.h instead of gfp.h

Indeed, I just saw your patch to fix this.

> 
> > Fixes: 36d4b36b6959 ("lib/nodemask: inline next_node_in() and
> > node_random()")
> 
> I think it rather fixes 38addce8b600ca33 ("gcc-plugins: Add
> latent_entropy plugin").

You're right, I was in a rush and should have tagged that
appropriately.

> 
> For the rest,
> Reviewed-by: Yury Norov <yury.norov@...il.com>

Thanks!


-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@...ux.ibm.com   IBM Australia Limited