linux-kernel - Re: [PATCH RESEND] drm/amd/display: avoid using null object of framebuffer

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Message-ID: <CADnq5_OzY97etD0LW5Tw-xCnnTYonGkvxA875xdAfMgxAtu_DQ@mail.gmail.com>
Date: Wed, 21 Aug 2024 16:22:10 -0400
From: Alex Deucher <alexdeucher@...il.com>
To: Ma Ke <make24@...as.ac.cn>
Cc: alexander.deucher@....com, christian.koenig@....com, Xinhui.Pan@....com, 
	airlied@...il.com, daniel@...ll.ch, mwen@...lia.com, aurabindo.pillai@....com, 
	joshua@...ggi.es, hamza.mahfooz@....com, marek.olsak@....com, 
	HaoPing.Liu@....com, akpm@...ux-foundation.org, amd-gfx@...ts.freedesktop.org, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	stable@...r.kernel.org
Subject: Re: [PATCH RESEND] drm/amd/display: avoid using null object of framebuffer

On Wed, Aug 21, 2024 at 3:45 AM Ma Ke <make24@...as.ac.cn> wrote:
>
> Instead of using state->fb->obj[0] directly, get object from framebuffer
> by calling drm_gem_fb_get_obj() and return error code when object is
> null to avoid using null object of framebuffer.
>
> Cc: stable@...r.kernel.org
> Fixes: 5d945cbcd4b1 ("drm/amd/display: Create a file dedicated to planes")
> Signed-off-by: Ma Ke <make24@...as.ac.cn>
> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
> index a83bd0331c3b..5cb11cc2d063 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
> @@ -28,6 +28,7 @@
>  #include <drm/drm_blend.h>
>  #include <drm/drm_gem_atomic_helper.h>
>  #include <drm/drm_plane_helper.h>
> +#include <drm/drm_gem_framebuffer_helper.h>
>  #include <drm/drm_fourcc.h>
>
>  #include "amdgpu.h"
> @@ -935,10 +936,14 @@ static int amdgpu_dm_plane_helper_prepare_fb(struct drm_plane *plane,
>         }
>
>         afb = to_amdgpu_framebuffer(new_state->fb);
> -       obj = new_state->fb->obj[0];
> +       obj = drm_gem_fb_get_obj(new_state->fb, 0);

Is it possible for obj to be NULL here?

Alex

> +       if (!obj) {
> +               DRM_ERROR("Failed to get obj from framebuffer\n");
> +               return -EINVAL;
> +       }
> +
>         rbo = gem_to_amdgpu_bo(obj);
>         adev = amdgpu_ttm_adev(rbo->tbo.bdev);
> -
>         r = amdgpu_bo_reserve(rbo, true);
>         if (r) {
>                 dev_err(adev->dev, "fail to reserve bo (%d)\n", r);
> --
> 2.25.1
>