Re: [PATCH net v3 3/4] net: dsa: microchip: Ensure a ksz_irq is initialized before freeing it

[Andrew Lunn <andrew@lunn.ch>]

On Fri, Nov 14, 2025 at 08:20:22AM +0100, Bastien Curutchet (Schneider Electric) wrote:
> Sometimes ksz_irq_free() can be called on uninitialized ksz_irq (for
> example when ksz_ptp_irq_setup() fails). It leads to freeing
> uninitialized IRQ numbers and/or domains.
> 
> Ensure that IRQ numbers or domains aren't null before freeing them.
> In our case the IRQ number of an initialized ksz_irq is never 0. Indeed,
> it's either the device's IRQ number and we enter the IRQ setup only when
> this dev->irq is strictly positive, or a virtual IRQ assigned with
> irq_create_mapping() which returns strictly positive IRQ numbers.
> 
> Fixes: cc13ab18b201 ("net: dsa: microchip: ptp: enable interrupt for timestamping")
> Signed-off-by: Bastien Curutchet (Schneider Electric) <bastien.curutchet@bootlin.com>
> --
> Regarding the Fixes tag here, IMO before cc13ab18b201 it was safe to
> not check the domain and the IRQ number because I don't see any path
> where ksz_irq_free() would be called on a non-initialized ksz_irq

I would say the caller is wrong, not ksz_irq_free().

Functions like this come in pairs: ksz_irq_setup() & ksz_irq_free().
_free() should not be called if _setup() was not successful.

Please take a look if you can fix the caller. If the change is big,
maybe we need this as a minimal fix for net, but make the bigger
change in net-next?

Thanks
	Andrew