[PATCH] drm/sun4i: backend: Fix error pointers in sun4i_backend_atomic_check

[Chenyuan Yang <chenyuan0y@gmail.com>]

The function sun4i_backend_atomic_check was dereferencing pointers
returned by drm_atomic_get_plane_state without checking for errors. This
could lead to undefined behavior if the function returns an error pointer.

This commit adds checks using IS_ERR to ensure that plane_state is
valid before dereferencing them.

Similar to commit da29abe71e16
("drm/amd/display: Fix error pointers in amdgpu_dm_crtc_mem_type_changed").

Fixes: 96180dde23b7 ("drm/sun4i: backend: Add a custom atomic_check for the frontend")
Signed-off-by: Chenyuan Yang <chenyuan0y@gmail.com>
---
 drivers/gpu/drm/sun4i/sun4i_backend.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c b/drivers/gpu/drm/sun4i/sun4i_backend.c
index 2dded3b828df..a8e0e2123764 100644
--- a/drivers/gpu/drm/sun4i/sun4i_backend.c
+++ b/drivers/gpu/drm/sun4i/sun4i_backend.c
@@ -490,6 +490,10 @@ static int sun4i_backend_atomic_check(struct sunxi_engine *engine,
 	drm_for_each_plane_mask(plane, drm, crtc_state->plane_mask) {
 		struct drm_plane_state *plane_state =
 			drm_atomic_get_plane_state(state, plane);
+
+		if (IS_ERR(plane_state))
+			return PTR_ERR(plane_state);
+
 		struct sun4i_layer_state *layer_state =
 			state_to_sun4i_layer_state(plane_state);
 		struct drm_framebuffer *fb = plane_state->fb;
-- 
2.34.1