[PATCH] drm/nouveau/disp: Fix nvif_outp_acquire_dp() argument size

[Lyude Paul]

Sorry! I've been pretty busy until now, this is:

Reviewed-by: Lyude Paul <lyude at redhat.com>

Let me know if you've pushed it already or if you want me to push it to drm-
misc

On Wed, 2023-01-25 at 12:15 -0800, Kees Cook wrote:
> Ping. I'll take this via my tree unless someone else wants to take it...
> 
> On Sun, Nov 27, 2022 at 10:30:41AM -0800, Kees Cook wrote:
> > Both Coverity and GCC with -Wstringop-overflow noticed that
> > nvif_outp_acquire_dp() accidentally defined its second argument with 1
> > additional element:
> > 
> > drivers/gpu/drm/nouveau/dispnv50/disp.c: In function 'nv50_pior_atomic_enable':
> > drivers/gpu/drm/nouveau/dispnv50/disp.c:1813:17: error: 'nvif_outp_acquire_dp' accessing 16 bytes in a region of size 15 [-Werror=stringop-overflow=]
> >  1813 |                 nvif_outp_acquire_dp(&nv_encoder->outp, nv_encoder->dp.dpcd, 0, 0, false, false);
> >       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/gpu/drm/nouveau/dispnv50/disp.c:1813:17: note: referencing argument 2 of type 'u8[16]' {aka 'unsigned char[16]'}
> > drivers/gpu/drm/nouveau/include/nvif/outp.h:24:5: note: in a call to function 'nvif_outp_acquire_dp'
> >    24 | int nvif_outp_acquire_dp(struct nvif_outp *, u8 dpcd[16],
> >       |     ^~~~~~~~~~~~~~~~~~~~
> > 
> > Avoid these warnings by defining the argument size using the matching
> > define (DP_RECEIVER_CAP_SIZE, 15) instead of having it be a literal
> > (and incorrect) value (16).
> > 
> > Reported-by: coverity-bot <keescook+coverity-bot at chromium.org>
> > Addresses-Coverity-ID: 1527269 ("Memory - corruptions")
> > Addresses-Coverity-ID: 1527268 ("Memory - corruptions")
> > Link: https://lore.kernel.org/lkml/202211100848.FFBA2432@keescook/
> > Link: https://lore.kernel.org/lkml/202211100848.F4C2819BB@keescook/
> > Fixes: 813443721331 ("drm/nouveau/disp: move DP link config into acquire")
> > Cc: Ben Skeggs <bskeggs at redhat.com>
> > Cc: Karol Herbst <kherbst at redhat.com>
> > Cc: Lyude Paul <lyude at redhat.com>
> > Cc: David Airlie <airlied at gmail.com>
> > Cc: Daniel Vetter <daniel at ffwll.ch>
> > Cc: Dave Airlie <airlied at redhat.com>
> > Cc: "Gustavo A. R. Silva" <gustavo at embeddedor.com>
> > Cc: dri-devel at lists.freedesktop.org
> > Cc: nouveau at lists.freedesktop.org
> > Signed-off-by: Kees Cook <keescook at chromium.org>
> > ---
> >  drivers/gpu/drm/nouveau/include/nvif/outp.h | 3 ++-
> >  drivers/gpu/drm/nouveau/nvif/outp.c         | 2 +-
> >  2 files changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/nouveau/include/nvif/outp.h b/drivers/gpu/drm/nouveau/include/nvif/outp.h
> > index 45daadec3c0c..fa76a7b5e4b3 100644
> > --- a/drivers/gpu/drm/nouveau/include/nvif/outp.h
> > +++ b/drivers/gpu/drm/nouveau/include/nvif/outp.h
> > @@ -3,6 +3,7 @@
> >  #define __NVIF_OUTP_H__
> >  #include <nvif/object.h>
> >  #include <nvif/if0012.h>
> > +#include <drm/display/drm_dp.h>
> >  struct nvif_disp;
> >  
> >  struct nvif_outp {
> > @@ -21,7 +22,7 @@ int nvif_outp_acquire_rgb_crt(struct nvif_outp *);
> >  int nvif_outp_acquire_tmds(struct nvif_outp *, int head,
> >  			   bool hdmi, u8 max_ac_packet, u8 rekey, u8 scdc, bool hda);
> >  int nvif_outp_acquire_lvds(struct nvif_outp *, bool dual, bool bpc8);
> > -int nvif_outp_acquire_dp(struct nvif_outp *, u8 dpcd[16],
> > +int nvif_outp_acquire_dp(struct nvif_outp *outp, u8 dpcd[DP_RECEIVER_CAP_SIZE],
> >  			 int link_nr, int link_bw, bool hda, bool mst);
> >  void nvif_outp_release(struct nvif_outp *);
> >  int nvif_outp_infoframe(struct nvif_outp *, u8 type, struct nvif_outp_infoframe_v0 *, u32 size);
> > diff --git a/drivers/gpu/drm/nouveau/nvif/outp.c b/drivers/gpu/drm/nouveau/nvif/outp.c
> > index 7da39f1eae9f..c24bc5eae3ec 100644
> > --- a/drivers/gpu/drm/nouveau/nvif/outp.c
> > +++ b/drivers/gpu/drm/nouveau/nvif/outp.c
> > @@ -127,7 +127,7 @@ nvif_outp_acquire(struct nvif_outp *outp, u8 proto, struct nvif_outp_acquire_v0
> >  }
> >  
> >  int
> > -nvif_outp_acquire_dp(struct nvif_outp *outp, u8 dpcd[16],
> > +nvif_outp_acquire_dp(struct nvif_outp *outp, u8 dpcd[DP_RECEIVER_CAP_SIZE],
> >  		     int link_nr, int link_bw, bool hda, bool mst)
> >  {
> >  	struct nvif_outp_acquire_v0 args;
> > -- 
> > 2.34.1
> > 
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat