Re: [PATCH net-next v3 11/13] net: dsa: rzn1-a5psw: Add fixed frame length workaround for management port

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] net: dsa: missing NULL check for of_device_get_match_data()
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commit 8d40702613d22f005a1af76ac95b3654ab3e2d50
Author: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>

net: dsa: rzn1-a5psw: Add fixed frame length workaround for management port

The ETHSW IP used in SoCs such as RZ/T2H and RZ/N2H has a hardware issue
where the internal mgmt_tag_vld signal is asserted as a level instead of
a single-cycle pulse. This causes the frame length counter on the
management (CPU) port to over-increment, so valid frames are falsely
detected as oversized and dropped.

> diff --git a/drivers/net/dsa/rzn1_a5psw.c b/drivers/net/dsa/rzn1_a5psw.c
> index 0b0b4055e6155..30eca64fb2183 100644
> --- a/drivers/net/dsa/rzn1_a5psw.c
> +++ b/drivers/net/dsa/rzn1_a5psw.c
> @@ -209,8 +209,13 @@ static int a5psw_port_enable(struct dsa_switch *ds, int port,
>  static int a5psw_port_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
>  {
>  	struct a5psw *a5psw = ds->priv;
> +	const struct a5psw_of_data *of_data = a5psw->of_data;
> +
> +	if (dsa_is_cpu_port(ds, port) && of_data->management_port_fixed_frame_len)
> +		return 0;

[Severity: Medium]
Since this code relies on a5psw->of_data, could there be a NULL pointer
dereference if the device is bound manually via sysfs without a matching
device tree node?

Looking at a5psw_probe() where a5psw->of_data is initialized:

	a5psw->of_data = of_device_get_match_data(dev);
	a5psw->bridged_ports = BIT(a5psw->of_data->cpu_port);

If a user with root privileges binds the driver via sysfs (using
driver_override and bind) without a matching device tree node,
of_device_get_match_data() returns NULL. Does this cause an immediate
crash when accessing cpu_port during probe?

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Sashiko AI review · https://sashiko.dev/#/patchset/20261014131906.990077-1-prabhakar.mahadev-lad.rj@bp.renesas.com?part=11