linux-kernel - Re: [PATCH] MIPS: ralink: Fix refcount leak in ill_acc_of

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Message-Id: <83B958C5-1C7B-43C4-9EA2-93F8705B31A8@linux.dev>
Date: Wed, 9 Apr 2025 16:16:59 +0200
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Jonas Gorski <jonas.gorski@...il.com>
Cc: John Crispin <john@...ozen.org>,
 Sergio Paracuellos <sergio.paracuellos@...il.com>,
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
 stable@...r.kernel.org,
 linux-mips@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: ralink: Fix refcount leak in ill_acc_of_setup()

On 9. Apr 2025, at 14:57, Jonas Gorski wrote:
> On Mon, Apr 7, 2025 at 10:32 AM Thorsten Blum wrote:
>> 
>> The of_find_device_by_node() function increments the reference count of
>> the embedded device, which should be released with put_device() when it
>> is no longer needed.
>> 
>> In ill_acc_of_setup(), put_device() is only called on error paths, but
>> not on the success path. Fix this by calling put_device() before
>> returning successfully.
> 
> I would think this is very much deliberate as the device is used as
> the priv argument of the registered IRQ handler. AFAIU as long as that
> one is live the reference of the device needs to be kept.
> 
> Dropping the reference of the device should only be done after
> freeing/unregistering the IRQ again, which currently never happens.

Thanks for the explanation. I assumed request_irq() would increment the
refcount, but that's apparently not the case because it's just a cookie.

Thanks,
Thorsten