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From:   Alex Deucher <alexdeucher@gmail.com>
Date:   Mon, 27 Sep 2021 15:20:12 -0400
Message-ID: <CADnq5_NcRQO=VAGONoBBebZAXXaNDshUZk9=RpLVu3LdGnztXA@mail.gmail.com>
Subject: Re: [PATCH] drm/amdgpu: fix warning for overflow check
To:     =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>
Cc:     Arnd Bergmann <arnd@kernel.org>,
        Alex Deucher <alexander.deucher@amd.com>,
        "Pan, Xinhui" <Xinhui.Pan@amd.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Chunming Zhou <david1.zhou@amd.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
        Maling list - DRI developers 
        <dri-devel@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>, llvm@lists.linux.dev
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Applied.  Thanks!

On Mon, Sep 27, 2021 at 9:07 AM Christian K=C3=B6nig
<christian.koenig@amd.com> wrote:
>
> Am 27.09.21 um 14:58 schrieb Arnd Bergmann:
> > From: Arnd Bergmann <arnd@arndb.de>
> >
> > The overflow check in amdgpu_bo_list_create() causes a warning with
> > clang-14 on 64-bit architectures, since the limit can never be
> > exceeded.
> >
> > drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c:74:18: error: result of com=
parison of constant 256204778801521549 with expression of type 'unsigned in=
t' is always false [-Werror,-Wtautological-constant-out-of-range-compare]
> >          if (num_entries > (SIZE_MAX - sizeof(struct amdgpu_bo_list))
> >              ~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > The check remains useful for 32-bit architectures, so just avoid the
> > warning by using size_t as the type for the count.
> >
> > Fixes: 920990cb080a ("drm/amdgpu: allocate the bo_list array after the =
list")
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>
> Reviewed-by: Christian K=C3=B6nig <christian.koenig@amd.com>
>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c | 2 +-
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h | 2 +-
> >   2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c b/drivers/gpu/=
drm/amd/amdgpu/amdgpu_bo_list.c
> > index 15c45b2a3983..714178f1b6c6 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
> > @@ -61,7 +61,7 @@ static void amdgpu_bo_list_free(struct kref *ref)
> >
> >   int amdgpu_bo_list_create(struct amdgpu_device *adev, struct drm_file=
 *filp,
> >                         struct drm_amdgpu_bo_list_entry *info,
> > -                       unsigned num_entries, struct amdgpu_bo_list **r=
esult)
> > +                       size_t num_entries, struct amdgpu_bo_list **res=
ult)
> >   {
> >       unsigned last_entry =3D 0, first_userptr =3D num_entries;
> >       struct amdgpu_bo_list_entry *array;
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h b/drivers/gpu/=
drm/amd/amdgpu/amdgpu_bo_list.h
> > index c905a4cfc173..044b41f0bfd9 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h
> > @@ -61,7 +61,7 @@ int amdgpu_bo_create_list_entry_array(struct drm_amdg=
pu_bo_list_in *in,
> >   int amdgpu_bo_list_create(struct amdgpu_device *adev,
> >                                struct drm_file *filp,
> >                                struct drm_amdgpu_bo_list_entry *info,
> > -                              unsigned num_entries,
> > +                              size_t num_entries,
> >                                struct amdgpu_bo_list **list);
> >
> >   static inline struct amdgpu_bo_list_entry *
>