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Subject: Re: [PATCH] MIPS: ralink: Fix refcount leak in ill_acc_of_setup()
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From: Thorsten Blum <thorsten.blum@linux.dev>
In-Reply-To: <CAOiHx==cJicn3fYbf+yOfGX1ORZNgBwUNuV-2CNAxmdpn9O5Ww@mail.gmail.com>
Date: Wed, 9 Apr 2025 16:16:59 +0200
Cc: John Crispin <john@phrozen.org>,
 Sergio Paracuellos <sergio.paracuellos@gmail.com>,
 Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
 stable@vger.kernel.org,
 linux-mips@vger.kernel.org,
 linux-kernel@vger.kernel.org
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References: <20250407082759.742105-1-thorsten.blum@linux.dev>
 <CAOiHx==cJicn3fYbf+yOfGX1ORZNgBwUNuV-2CNAxmdpn9O5Ww@mail.gmail.com>
To: Jonas Gorski <jonas.gorski@gmail.com>
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On 9. Apr 2025, at 14:57, Jonas Gorski wrote:
> On Mon, Apr 7, 2025 at 10:32=E2=80=AFAM Thorsten Blum wrote:
>>=20
>> 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.
>>=20
>> 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.
>=20
> 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.
>=20
> 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