[PATCH] drm/sti: avoid potential dereference of error pointers in sti_hqvdp_atomic_check

[Ma Ke <make24@xxxxxxxxxxx>]

The return value of drm_atomic_get_crtc_state() needs to be
checked. To avoid use of error pointer 'crtc_state' in case
of the failure.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: dd86dc2f9ae1 ("drm/sti: implement atomic_check for the planes")
Signed-off-by: Ma Ke <make24@xxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20240913090926.2023716-1-make24@xxxxxxxxxxx
Signed-off-by: Alain Volmat <alain.volmat@xxxxxxxxxxx>

diff --git a/drivers/gpu/drm/sti/sti_hqvdp.c b/drivers/gpu/drm/sti/sti_hqvdp.c
index acbf70b95aeb..5793cf2cb897 100644
--- a/drivers/gpu/drm/sti/sti_hqvdp.c
+++ b/drivers/gpu/drm/sti/sti_hqvdp.c
@@ -1037,6 +1037,9 @@ static int sti_hqvdp_atomic_check(struct drm_plane *drm_plane,
 		return 0;
 
 	crtc_state = drm_atomic_get_crtc_state(state, crtc);
+	if (IS_ERR(crtc_state))
+		return PTR_ERR(crtc_state);
+
 	mode = &crtc_state->mode;
 	dst_x = new_plane_state->crtc_x;
 	dst_y = new_plane_state->crtc_y;