Re: linux-next: build warning after merge of the kspp tree

Kees Cook
2021-09-06T17:06:14Z

On Mon, Sep 06, 2021 at 03:41:51PM +1000, Stephen Rothwell wrote:
> Hi all,
>
> On Mon, 30 Aug 2021 18:44:29 +1000 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> >
> > After merging the kspp tree, today's linux-next build (powerpc
> > allyesconfig) produced this warning:
> >
> > drivers/gpu/drm/kmb/kmb_plane.c:135:20: warning: array subscript 3 is above array bounds of 'struct layer_status[1]' [-Warray-bounds]
> > 135 | kmb->plane_status[plane_id].ctrl = LCD_CTRL_GL2_ENABLE;
> > | ~~~~~~~~~~~~~~~~~^~~~~~~~~~
> > In file included from drivers/gpu/drm/kmb/kmb_plane.c:17:
> > drivers/gpu/drm/kmb/kmb_drv.h:48:23: note: while referencing 'plane_status'
> > 48 | struct layer_status plane_status[KMB_MAX_PLANES];
> > | ^~~~~~~~~~~~
> > drivers/gpu/drm/kmb/kmb_plane.c:132:20: warning: array subscript 2 is above array bounds of 'struct layer_status[1]' [-Warray-bounds]
> > 132 | kmb->plane_status[plane_id].ctrl = LCD_CTRL_GL1_ENABLE;
> > | ~~~~~~~~~~~~~~~~~^~~~~~~~~~
> > In file included from drivers/gpu/drm/kmb/kmb_plane.c:17:
> > drivers/gpu/drm/kmb/kmb_drv.h:48:23: note: while referencing 'plane_status'
> > 48 | struct layer_status plane_status[KMB_MAX_PLANES];
> > | ^~~~~~~~~~~~
> > drivers/gpu/drm/kmb/kmb_plane.c:129:20: warning: array subscript 1 is above array bounds of 'struct layer_status[1]' [-Warray-bounds]
> > 129 | kmb->plane_status[plane_id].ctrl = LCD_CTRL_VL2_ENABLE;
> > | ~~~~~~~~~~~~~~~~~^~~~~~~~~~
> > In file included from drivers/gpu/drm/kmb/kmb_plane.c:17:
> > drivers/gpu/drm/kmb/kmb_drv.h:48:23: note: while referencing 'plane_status'
> > 48 | struct layer_status plane_status[KMB_MAX_PLANES];
> > | ^~~~~~~~~~~~
> >
> > Exposed by commit
> >
> > 656256c0d67c ("Makefile: Enable -Warray-bounds")
> >
> > Introduced by commit
> >
> > 7f7b96a8a0a1 ("drm/kmb: Add support for KeemBay Display")
> >
> > from v5.11-rc1.
>
> Due to Linus -Werror, these are now errors :-(
>
> I have reverted commit 656256c0d67c for now.

I'm still surprised Linus added -Werror (it seems to go against years of
his earlier mandates on not breaking the build). Seems like
3fe617ccafd6 should be reverted instead. ;)

Linus, warnings are being reported (as above), are you sure -Werror is
the right way to go? (I can't believe I'm saying this, given my past
desire to make various hardening failures break the build -- you
convinced me to always warn instead, and it made good sense: a developer
still gets binary results as well as any new warnings...)

-Kees

--
Kees Cook