linux-kernel - Re: [PATCH net v3 3/4] net: dsa: microchip: Ensure a ksz

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Message-ID: <dc492850-6e6b-4c2e-9869-321045c1f1c1@bootlin.com>
Date: Mon, 17 Nov 2025 09:51:50 +0100
From: Bastien Curutchet <bastien.curutchet@...tlin.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Woojung Huh <woojung.huh@...rochip.com>, UNGLinuxDriver@...rochip.com,
 Vladimir Oltean <olteanv@...il.com>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Richard Cochran <richardcochran@...il.com>,
 Arun Ramadoss <arun.ramadoss@...rochip.com>,
 Pascal Eberhard <pascal.eberhard@...com>,
 Miquèl Raynal <miquel.raynal@...tlin.com>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v3 3/4] net: dsa: microchip: Ensure a ksz_irq is
 initialized before freeing it

Hi Andrew,

On 11/14/25 4:00 PM, Andrew Lunn wrote:
> 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@...tlin.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?

Ok, I'll look at it, I think the change won't be that big.

Best regards,
Bastien