linux-kernel - Re: [PATCH] can: j1939: call j1939_priv_put() immediately when j1939_local_ecu

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Message-ID: <aKwqCYaDf-zYzbtT@pengutronix.de>
Date: Mon, 25 Aug 2025 11:16:57 +0200
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc: Robin van der Gracht <robin@...tonic.nl>, kernel@...gutronix.de,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	Marc Kleine-Budde <mkl@...gutronix.de>, linux-can@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] can: j1939: call j1939_priv_put() immediately when
 j1939_local_ecu_get() failed

Hi Tetsuo,

On Sun, Aug 24, 2025 at 07:30:09PM +0900, Tetsuo Handa wrote:
> Commit 25fe97cb7620 ("can: j1939: move j1939_priv_put() into sk_destruct
> callback") expects that a call to j1939_priv_put() can be unconditionally
> delayed until j1939_sk_sock_destruct() is called. But a refcount leak will
> happen when j1939_sk_bind() is called again after j1939_local_ecu_get()
>  from previous j1939_sk_bind() call returned an error. We need to call
> j1939_priv_put() before j1939_sk_bind() returns an error.
> 
> Fixes: 25fe97cb7620 ("can: j1939: move j1939_priv_put() into sk_destruct callback")
> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> ---
> The change made by commit 25fe97cb7620 might be relevant to my result
> 
>   As far as I tested, the only way that can drop the refcount to 1 is to
>   call j1939_sk_release() (which involves sock_put()) on all j1939 sockets
> 
> in https://lkml.kernel.org/r/bb595640-0597-4d18-a9e1-f6eb8e6bb50e@I-love.SAKURA.ne.jp .

Thank you for your work!
Right now I'm on open source summit and can't quickly respond/test your
patches. I'll try to do my best ASAP next week. 

Best Regards,
Oleksij
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