Re: [PATCH v7 4/7] nvmem: layouts: add Microchip/SST SFDP EUI layout driver

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Unloading the `microchip-sst26vf-sfdp-eui` module leaves a dangling `read_post_process` function pointer in the NVMEM core, leading to a kernel panic when the cell is subsequently read.
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--- Patch [4]: [PATCH v7 4/7] nvmem: layouts: add Microchip/SST SFDP EUI layout driver ---
commit ede7813294e82294452049f0c0c040524f47bb8e
Author: Manikandan Muralidharan <[email protected]>

nvmem: layouts: add Microchip/SST SFDP EUI layout driver

This commit adds an NVMEM layout driver for Microchip/SST SFDP flashes.
It locates the vendor-specific parameter table at runtime and exposes the
EUI-48 identifier as an NVMEM cell to be used as a MAC address.

> diff --git a/drivers/nvmem/layouts/sst26vf-sfdp-eui.c b/drivers/nvmem/layouts/sst26vf-sfdp-eui.c
> new file mode 100644
> index 0000000000000..641318d6f0af6
> --- /dev/null
> +++ b/drivers/nvmem/layouts/sst26vf-sfdp-eui.c
[ ... ]
> +static int sfdp_eui_add_cells(struct nvmem_layout *layout)
> +{
[ ... ]
> +	info.name = "mac-address";
> +	info.offset = base + SFDP_MCHP_EUI48_OFFSET;
> +	info.bytes = ETH_ALEN;
> +	info.np = of_get_child_by_name(layout_np, "mac-address");
> +	info.read_post_process = sfdp_eui_read_post_process;
> +
> +	ret = nvmem_add_one_cell(nvmem, &info);

[Severity: High]
Does registering this read_post_process callback create a dangling pointer
when the module is unloaded?

[ ... ]
> +static void sfdp_eui_remove(struct nvmem_layout *layout)
> +{
> +	nvmem_layout_unregister(layout);
> +}

[Severity: High]
Can unloading this module lead to a kernel panic?

Because nvmem_layout_unregister() is an empty stub in the NVMEM core, the
cells added by this layout are never removed.

If the module is unloaded, the sysfs entry for the cell remains active.
A subsequent read of the sysfs file will invoke the read_post_process
callback, which now points to freed module memory, causing a panic.

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Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=4