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

[Kees Cook <keescook@chromium.org>]

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@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@redhat.com>
> Cc: Karol Herbst <kherbst@redhat.com>
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: David Airlie <airlied@gmail.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Dave Airlie <airlied@redhat.com>
> Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
> Cc: dri-devel@lists.freedesktop.org
> Cc: nouveau@lists.freedesktop.org
> Signed-off-by: Kees Cook <keescook@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
> 

-- 
Kees Cook