Re: [PATCH RESEND] drm/stm: ltdc: fix late dereference check

From: Philippe CORNU
Date: Fri May 26 2023 - 07:41:05 EST

On 5/15/23 14:38, Raphael Gallais-Pou wrote:
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@xxxxxxxxx>
Reported-by: Dan Carpenter <error27@xxxxxxxxx>
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 03c6becda795..b8be4c1db423 100644
--- 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;
@@ -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);

Hi Raphael,
Applied on drm-misc-next.

Note & fyi, I fixed the following warning, please be sure to follow this rule next time :-)
WARNING:BAD_REPORTED_BY_LINK: Reported-by: should be immediately followed by Closes: with a URL to the report

Many thanks for your patch,
Philippe :-)