Date:   Fri, 27 Jan 2023 11:42:23 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Lyude Paul <lyude@redhat.com>
Cc:     Ben Skeggs <bskeggs@redhat.com>, Karol Herbst <kherbst@redhat.com>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Dave Airlie <airlied@redhat.com>,
        "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
        dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] drm/nouveau/disp: Fix nvif_outp_acquire_dp() argument
 size
Message-ID: <202301271141.6741F43@keescook>
References: <20221127183036.never.139-kees@kernel.org>
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On Wed, Jan 25, 2023 at 04:24:19PM -0500, Lyude Paul wrote:
> Sorry! I've been pretty busy until now, this is:
> 
> Reviewed-by: Lyude Paul <lyude@redhat.com>
> 
> Let me know if you've pushed it already or if you want me to push it to drm-
> misc

Either way is fine. I'm currently carrying it, but I can easily drop it
if you prefer it go via drm-misc.

Thanks!

-Kees

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

-- 
Kees Cook