Re: [PATCH 2/4] 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] Blind dereference of `dev->parent->parent` can lead to a kernel panic if the device is not instantiated with the expected MFD hierarchy.
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commit 227574270c722d2b535d72fadcf31ba55bc47f8e
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. It introduces a new nvmem driver that reads 24 bytes of
hardware-related data using regmap over the PMIC wrapper.

> diff --git a/drivers/nvmem/mt6323-efuse.c b/drivers/nvmem/mt6323-efuse.c
> new file mode 100644
> index 0000000000000..c6fbfd96ac047
> --- /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]
Is it possible for dev->parent to be NULL here?

Because the driver defines an of_match_table, it might be instantiated directly
by the OF core or bound manually via sysfs, bypassing the MFD subsystem.

If dev->parent is NULL, evaluating dev->parent->parent will cause an immediate
NULL pointer dereference. Furthermore, if dev->parent is valid but has no
parent, dev->parent->parent evaluates to NULL. Passing a NULL device pointer to
dev_get_regmap() causes a fatal NULL pointer dereference inside devres_find()
when it attempts to acquire the devres_lock.

Would it be safer to explicitly verify that both dev->parent and
dev->parent->parent are non-NULL before dereferencing them?

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

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Sashiko AI review · https://sashiko.dev/#/patchset/20260611-mt6323-nvmem-v1-0-b5e1b9ce51f2@protonmail.com?part=2