Re: [PATCH v7 3/7] mtd: spi-nor: sfdp: expose the SFDP as a read-only NVMEM device

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Use-After-Free of device tree node in NVMEM device due to premature of_node_put().
--

--- Patch [3]: [PATCH v7 3/7] mtd: spi-nor: sfdp: expose the SFDP as a read-only NVMEM device ---
commit d892664b27bcd5da338917980297630345d51e30
Author: Manikandan Muralidharan <[email protected]>

mtd: spi-nor: sfdp: expose the SFDP as a read-only NVMEM device

This commit exposes the cached SFDP table as a read-only NVMEM device
in on-flash byte order. The NVMEM device is registered only when an
sfdp node is present in the device tree.

> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index ccf4396cdcd04..0425af6e898fd 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c

[ ... ]

> @@ -3001,6 +3002,75 @@ static void spi_nor_init_fixup_flags(struct spi_nor *nor)
> +static int spi_nor_register_sfdp_nvmem(struct spi_nor *nor)
> +{

[ ... ]

> +	config.dev = dev;
> +	config.of_node = np;
> +	config.name = "sfdp";
> +	config.id = NVMEM_DEVID_AUTO;
> +	config.owner = THIS_MODULE;
> +	config.read_only = true;
> +	config.word_size = 1;
> +	config.stride = 1;
> +	config.size = (int)(nor->sfdp->num_dwords * sizeof(*nor->sfdp->dwords));
> +	config.reg_read = spi_nor_sfdp_reg_read;
> +	config.priv = nor;
> +
> +	nvmem = devm_nvmem_register(dev, &config);
> +	of_node_put(np);

[Severity: High]
Does calling of_node_put() here leave the NVMEM device with a dangling
pointer to the device tree node?

The nvmem core assigns config.of_node to the underlying device structure
but does not take an additional reference count on the node itself. 

If a device tree overlay is removed later, causing the node's reference
count to drop to zero, could this lead to a use-after-free when the nvmem
framework or sysfs subsequently accesses the node?

> +	if (IS_ERR(nvmem)) {
> +		/* NVMEM support is optional. */

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=3