drm/stm: ltdc: fix late dereference check

In ltdc_crtc_set_crc_source(), struct drm_crtc was dereferenced in a
container_of() before the pointer check. This could cause a kernel panic.

Fix this smatch warning:
drivers/gpu/drm/stm/ltdc.c:1124 ltdc_crtc_set_crc_source() warn: variable dereferenced before check 'crtc' (see line 1119)

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/lkml/202212241802.zeLFZCXB-lkp@intel.com/
Reported-by: Dan Carpenter <error27@gmail.com>
Closes: https://lore.kernel.org/lkml/202212241802.zeLFZCXB-lkp@intel.com/
Signed-off-by: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>
Acked-by: Philippe Cornu <philippe.cornu@foss.st.com>
Signed-off-by: Philippe Cornu <philippe.cornu@foss.st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230515123818.93971-1-raphael.gallais-pou@foss.st.com

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 03c6becda795c2b1f9ea907496eb068ef47846ee..b8be4c1db4235233fe4e7d23a5649410a667fbee 100644 (file)
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -1145,7 +1145,7 @@ 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");
@@ -1153,6 +1153,8 @@ 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);