[PATCH] drm/stm: ltdc: fix unchecked dereferenced pointer

[Raphael Gallais-Pou]

Pointer of struct *drm_crtc was dereferenced before checking it was non
NULL. This could potentially create a kernel panic.

Fixes: 79b44684a14e ("drm/stm: ltdc: add support for CRC hashing feature")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Raphael Gallais-Pou <raphael.gallais-pou@xxxxxxxxxxx>
---
 drivers/gpu/drm/stm/ltdc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 6bd45df8f5a7..9c0fadd58d2a 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -1120,7 +1120,7 @@ static void ltdc_crtc_disable_vblank(struct drm_crtc *crtc)
 
 static int ltdc_crtc_set_crc_source(struct drm_crtc *crtc, const char *source)
 {
-	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
+	struct ltdc_device *ldev;
 	int ret;
 
 	DRM_DEBUG_DRIVER("\n");
@@ -1128,6 +1128,8 @@ static int ltdc_crtc_set_crc_source(struct drm_crtc *crtc, const char *source)
 	if (!crtc)
 		return -ENODEV;
 
+	ldev = crtc_to_ltdc(crtc);
+
 	if (source && strcmp(source, "auto") == 0) {
 		ldev->crc_active = true;
 		ret = regmap_set_bits(ldev->regmap, LTDC_GCR, GCR_CRCEN);
-- 
2.25.1