[PATCH 5.3 33/95] drm/i915: Dont oops in dumb_create ioctl if we have no crtcs

[Greg Kroah-Hartman]

From: Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>

commit 8ac495f624a42809000255955be406f6a8a74b55 upstream.

Make sure we have a crtc before probing its primary plane's
max stride. Initially I thought we can't get this far without
crtcs, but looks like we can via the dumb_create ioctl.

Not sure if we shouldn't disable dumb buffer support entirely
when we have no crtcs, but that would require some amount of work
as the only thing currently being checked is dev->driver->dumb_create
which we'd have to convert to some device specific dynamic thing.

Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
Fixes: aa5ca8b7421c ("drm/i915: Align dumb buffer stride to 4k to allow for gtt remapping")
Signed-off-by: Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20191106172349.11987-1-ville.syrjala@xxxxxxxxxxxxxxx
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
(cherry picked from commit baea9ffe64200033499a4955f431e315bb807899)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
(cherry picked from commit aeec766133f99d45aad60d650de50fb382104d95)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/i915/display/intel_display.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -2519,6 +2519,9 @@ u32 intel_plane_fb_max_stride(struct drm
 	 * the highest stride limits of them all.
 	 */
 	crtc = intel_get_crtc_for_pipe(dev_priv, PIPE_A);
+	if (!crtc)
+		return 0;
+
 	plane = to_intel_plane(crtc->base.primary);
 
 	return plane->max_stride(plane, pixel_format, modifier,