[PATCH] pinctrl: intel: zero-initialize capability_offset[] in probe

[Stepan Ionichev <sozdayvek@gmail.com>]

intel_pinctrl_probe() declares a per-community capability_offset[]
array on the stack and only writes the slots whose CAPLIST entries
the device actually advertises:

	unsigned short capability_offset[6];
	...
	do {
		value = readl(regs + offset);
		switch ((value & CAPLIST_ID_MASK) >> CAPLIST_ID_SHIFT) {
		case CAPLIST_ID_GPIO_HW_INFO:
			capability_offset[CAPLIST_ID_GPIO_HW_INFO] = offset;
			break;
		case CAPLIST_ID_PWM:
			capability_offset[CAPLIST_ID_PWM] = offset;
			break;
		...
		default:
			break;
		}
		...
	} while (offset);

	...
	ret = intel_pinctrl_probe_pwm(pctrl, community,
				      capability_offset[CAPLIST_ID_PWM]);

If a community does not advertise a PWM capability, the loop never
writes capability_offset[CAPLIST_ID_PWM] and the call to
intel_pinctrl_probe_pwm() reads an indeterminate stack value.

intel_pinctrl_probe_pwm() computes the PWM register base before it
checks PINCTRL_FEATURE_PWM:

	void __iomem *base = community->regs + capability_offset + 4;
	...
	if (!(community->features & PINCTRL_FEATURE_PWM))
		return 0;

so the base = community->regs + capability_offset + 4 expression is
evaluated using the uninitialized value on every probe for any
community that does not have CAPLIST_ID_PWM. The result is never
dereferenced when the PWM feature flag is clear, but reading an
indeterminate stack object is undefined behaviour by C, and KMSAN /
UBSAN report it at probe time.

Default the whole array to zero at declaration so unused slots are
defined (community->regs + 4) instead of indeterminate.

Fixes: 340bba73c545 ("pinctrl: intel: Improve capability support")
Signed-off-by: Stepan Ionichev <sozdayvek@gmail.com>
---
 drivers/pinctrl/intel/pinctrl-intel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pinctrl/intel/pinctrl-intel.c b/drivers/pinctrl/intel/pinctrl-intel.c
index 97bf5ec78..4fb4a3dab 100644
--- a/drivers/pinctrl/intel/pinctrl-intel.c
+++ b/drivers/pinctrl/intel/pinctrl-intel.c
@@ -1601,7 +1601,7 @@ int intel_pinctrl_probe(struct platform_device *pdev,
 
 	for (i = 0; i < pctrl->ncommunities; i++) {
 		struct intel_community *community = &pctrl->communities[i];
-		unsigned short capability_offset[6];
+		unsigned short capability_offset[6] = { };
 		void __iomem *regs;
 		u32 revision;
 		u32 offset;
-- 
2.43.0