[v3,1/3] drm/framebuffer: Check for valid formats

Commit Message

Maíra Canal Jan. 13, 2023, 4:59 p.m. UTC

Currently, framebuffer_check() doesn't check if the pixel format is
supported, which can lead to the acceptance of invalid pixel formats
e.g. the acceptance of invalid modifiers. Therefore, add a check for
valid formats on framebuffer_check(), so that the ADDFB2 IOCTL rejects
calls with invalid formats.

Moreover, note that this check is only valid for atomic drivers,
because, for non-atomic drivers, checking drm_any_plane_has_format() is
not possible since the format list for the primary plane is fake, and
we'd therefore reject valid formats.

Reviewed-by: Daniel Vetter <[e-mail]>
Signed-off-by: Maíra Canal <[e-mail]>
---
 Documentation/gpu/todo.rst        | 9 ++++-----
 drivers/gpu/drm/drm_framebuffer.c | 8 ++++++++
 2 files changed, 12 insertions(+), 5 deletions(-)

Comments

Simon Ser Jan. 13, 2023, 5:04 p.m. UTC | #1

On Friday, January 13th, 2023 at 17:59, Maíra Canal <[e-mail]> wrote:

> +	/* Verify that the modifier is supported. */
> +	if (r->modifier[0] && drm_drv_uses_atomic_modeset(dev) &&
> +	    !drm_any_plane_has_format(dev, r->pixel_format, r->modifier[0])) {
> +		drm_dbg_kms(dev, "Unsupported pixel format %p4cc / modifier 0x%llx\n",
> +			    &r->pixel_format, r->modifier[0]);
> +		return -EINVAL;
> +	}

User-space indicates whether there is a modifier in the IOCTL data by supplying
the DRM_MODE_FB_MODIFIERS flag. I believe we need to check that flag instead of
r->modifier[0]: the zero modifier is a valid modifier (LINEAR).

Patch

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 1f8a5ebe188e..3a79c26c5cc7 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -276,11 +276,10 @@  Various hold-ups:
 - Need to switch to drm_fbdev_generic_setup(), otherwise a lot of the custom fb
   setup code can't be deleted.
 
-- Many drivers wrap drm_gem_fb_create() only to check for valid formats. For
-  atomic drivers we could check for valid formats by calling
-  drm_plane_check_pixel_format() against all planes, and pass if any plane
-  supports the format. For non-atomic that's not possible since like the format
-  list for the primary plane is fake and we'd therefor reject valid formats.
+- Need to switch to drm_gem_fb_create(), as now framebuffer_check() checks for
+  valid formats for atomic drivers.
+
+- Add an addfb format validation for non-atomic drivers.
 
 - Many drivers subclass drm_framebuffer, we'd need a embedding compatible
   version of the varios drm_gem_fb_create functions. Maybe called
diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
index aff3746dedfb..0afc9e39188a 100644
--- a/drivers/gpu/drm/drm_framebuffer.c
+++ b/drivers/gpu/drm/drm_framebuffer.c
@@ -280,6 +280,14 @@  static int framebuffer_check(struct drm_device *dev,
 		}
 	}
 
+	/* Verify that the modifier is supported. */
+	if (r->modifier[0] && drm_drv_uses_atomic_modeset(dev) &&
+	    !drm_any_plane_has_format(dev, r->pixel_format, r->modifier[0])) {
+		drm_dbg_kms(dev, "Unsupported pixel format %p4cc / modifier 0x%llx\n",
+			    &r->pixel_format, r->modifier[0]);
+		return -EINVAL;
+	}
+
 	return 0;
 }