Re: [PATCH v3 2/3] nvmem: add mt6323 PMIC EFUSE driver

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The driver blindly dereferences `dev->parent->parent` to retrieve the regmap, which causes a NULL pointer dereference kernel panic if instantiated outside the expected MFD hierarchy, and violates MFD subsystem guidelines.
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--- Patch [2]: [PATCH v3 2/3] nvmem: add mt6323 PMIC EFUSE driver ---
commit 25fbde0741e1e6a18bf5c1f7cc92f4eb70b9d17e
Author: Roman Vivchar <rva333@protonmail.com>

nvmem: add mt6323 PMIC EFUSE driver

This commit adds support for the EFUSE controller found in the Mediatek
MT6323 PMIC, which stores 24 bytes of hardware-related data.

> diff --git a/drivers/nvmem/mt6323-efuse.c b/drivers/nvmem/mt6323-efuse.c
> new file mode 100644
> index 0000000000000..41678915d5b62
> --- /dev/null
> +++ b/drivers/nvmem/mt6323-efuse.c

[ ... ]

> +static int mt6323_efuse_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct nvmem_config config = {
> +		.name = "mt6323-efuse",
> +		.stride = 2,
> +		.word_size = 2,
> +		.size = MT6323_EFUSE_SIZE,
> +		.reg_read = mt6323_efuse_read,
> +	};
> +	struct nvmem_device *nvmem;
> +	struct regmap *regmap;
> +
> +	/* efuse -> mfd -> pwrap */
> +	regmap = dev_get_regmap(dev->parent->parent, NULL);

[Severity: High]
Can this cause a NULL pointer dereference if the device is instantiated
outside the expected MFD hierarchy?

If the device is instantiated directly via a Device Tree root node overlay or
through sysfs, dev->parent could be the platform_bus. Because the
platform_bus has no parent, evaluating dev->parent->parent would result in
NULL. 

Passing NULL to dev_get_regmap() leads to an immediate kernel panic when
devres_find() unconditionally locks the devres_lock.

Additionally, MFD subsystem guidelines recommend that child drivers retrieve
data using standard APIs without relying on hard-coded assumptions about
grandparent device topology.

> +	if (!regmap)
> +		return dev_err_probe(dev, -ENODEV, "failed to get regmap\n");
> +
> +	config.dev = dev;
> +	config.priv = regmap;

[ ... ]

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Sashiko AI review · https://sashiko.dev/#/patchset/20260713-mt6323-nvmem-v3-0-205c39267a24@protonmail.com?part=2