Re: [PATCH iwl-next v4] igc: Support ACPI-based MAC passthrough

[Simon Horman <horms@kernel.org>]

This is an AI-generated review of your patch. The human sending this
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Full review at: https://sashiko.dev/#/patchset/20260910193824.3257378-1-dima.ruinskiy@intel.com?part=1
---
igc: Support ACPI-based MAC passthrough

This commit implements support for seamlessly passing through a system MAC
address provided in the ACPI table to an I225/I226 network controller
attached via a Thunderbolt dock.

> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 1fb5f3cbe93c5..abffd385f3e8c 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
[ ... ]
> @@ -7106,6 +7108,58 @@ static enum hrtimer_restart igc_qbv_scheduling_timer(struct hrtimer *timer)
>  	return HRTIMER_NORESTART;
>  }
>  
> +static bool igc_get_acpi_mac_passthru(u8 *mac)
> +{
[ ... ]
> +	acpi_status status;
> +	u8 buf[ETH_ALEN];

[Severity: High]
Does this array lack a 16-bit alignment guarantee? 

Because it is declared as a simple byte array on the stack, the compiler is
free to place it at an odd memory address.

> +	int i;
> +
> +	if (!IS_ENABLED(CONFIG_ACPI))
> +		return false;
> +
> +	for (i = 0; i < ARRAY_SIZE(sources) && !mac_found; i++) {
[ ... ]
> +		if (hex2bin(buf, obj->string.pointer + 9, ETH_ALEN) ||
> +		    !is_valid_ether_addr(buf))
> +			goto free_obj;
> +
> +		ether_addr_copy(mac, buf);

[Severity: High]
Can passing this buffer to is_valid_ether_addr() and ether_addr_copy() cause
an alignment trap on architectures that strictly enforce memory alignment?

Both of these helpers cast the pointer to a u16 pointer to perform 16-bit
memory operations when CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is not set. 
If buf ends up placed at an odd address, this could cause a kernel panic.

Could this be avoided by defining buf as a u16 array or by adding an explicit
__aligned(2) attribute?

> +		mac_found = true;
> +free_obj:
> +		ACPI_FREE(obj);
> +	}
> +
> +	return mac_found;
> +}
> +