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

From: Dan Carpenter
Date: Sat Dec 24 2022 - 06:04:37 EST


tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 72a85e2b0a1e1e6fb4ee51ae902730212b2de25c
commit: 79b44684a14e363d24c299b772f037344ad8c8dc drm/stm: ltdc: add support for CRC hashing feature
config: arm-randconfig-m041-20221224
compiler: arm-linux-gnueabi-gcc (GCC) 12.1.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Reported-by: Dan Carpenter <error27@xxxxxxxxx>

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

Old smatch warnings:
drivers/gpu/drm/stm/ltdc.c:901 ltdc_crtc_mode_set_nofb() warn: iterator used outside loop: 'bridge'
drivers/gpu/drm/stm/ltdc.c:911 ltdc_crtc_mode_set_nofb() warn: pm_runtime_get_sync() also returns 1 on success

vim +/crtc +1124 drivers/gpu/drm/stm/ltdc.c

79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1117 static int ltdc_crtc_set_crc_source(struct drm_crtc *crtc, const char *source)
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1118 {
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 @1119 struct ltdc_device *ldev = crtc_to_ltdc(crtc);
^^^^
Derefernce

79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1120 int ret;
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1121
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1122 DRM_DEBUG_DRIVER("\n");
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1123
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 @1124 if (!crtc)
^^^^^
Checked too late.

79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1125 return -ENODEV;
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1126
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1127 if (source && strcmp(source, "auto") == 0) {
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1128 ldev->crc_active = true;
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1129 ret = regmap_set_bits(ldev->regmap, LTDC_GCR, GCR_CRCEN);
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1130 } else if (!source) {
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1131 ldev->crc_active = false;
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1132 ret = regmap_clear_bits(ldev->regmap, LTDC_GCR, GCR_CRCEN);
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1133 } else {
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1134 ret = -EINVAL;
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1135 }
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1136
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1137 ldev->crc_skip_count = 0;
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1138 return ret;
79b44684a14e36 Raphael Gallais-Pou 2022-02-11 1139 }

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