Re: [PATCH v4 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] NULL pointer dereference when accessing `dev->parent->parent` to retrieve the regmap.
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commit 9cacac916b33064bc7243868fd8890da0759dff1
Author: Roman Vivchar <rva333@protonmail.com>

nvmem: add mt6323 PMIC EFUSE driver

Add support for the EFUSE controller found in the Mediatek MT6323 PMIC.
The MT6323 EFUSE stores 24 bytes of hardware-related data, such as
thermal sensor calibration values.

> diff --git a/drivers/nvmem/mt6323-efuse.c b/drivers/nvmem/mt6323-efuse.c
> new file mode 100644
> index 0000000000000..6f6f1cdc2f388
> --- /dev/null
> +++ b/drivers/nvmem/mt6323-efuse.c
[ ... ]
> @@ -0,0 +1,84 @@
[ ... ]
> +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]
Does this code safely handle cases where the device hierarchy is shallower
than expected?

If the device is instantiated without a grandparent (for example, via a
malformed device tree overlay or manually created via sysfs), dev->parent
will point to the platform_bus, and dev->parent->parent will be NULL.

Passing NULL to dev_get_regmap() forwards it to devres_find(), which then
dereferences the NULL pointer when attempting to take the device's resource
lock.

Additionally, if dev->parent itself is ever NULL, evaluating
dev->parent->parent will crash before the function call even occurs.

> +	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/20260911-mt6323-nvmem-v4-0-626dd17531dc@protonmail.com?part=2