linux-kernel - Re: [PATCH] serial: core: Fix kmemleak issue for serial core device remove

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Message-ID: <20230804092105.GI14799@atomide.com>
Date:   Fri, 4 Aug 2023 12:21:05 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Jiri Slaby <jirislaby@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Dhruva Gole <d-gole@...com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        John Ogness <john.ogness@...utronix.de>,
        Johan Hovold <johan@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Subject: Re: [PATCH] serial: core: Fix kmemleak issue for serial core device
 remove

* Jiri Slaby <jirislaby@...nel.org> [230804 09:16]:
> On 04. 08. 23, 11:09, Tony Lindgren wrote:
> > Kmemleak reports issues for serial8250 ports after the hardware specific
> > driver takes over on boot as noted by Tomi.
> > 
> > The kerneldoc for device_initialize() says we must call device_put()
> > after calling device_initialize(). We are calling device_put() on the
> > error path, but are missing it from the device remove path. This causes
> > release() to never get called for the devices on remove.
> > 
> > Let's add the missing put_device() calls for both serial ctrl and
> > port devices.
> > 
> > Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM")
> > Reported-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> > Signed-off-by: Tony Lindgren <tony@...mide.com>
> > ---
> >   drivers/tty/serial/serial_base_bus.c | 2 ++
> >   1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/tty/serial/serial_base_bus.c b/drivers/tty/serial/serial_base_bus.c
> > --- a/drivers/tty/serial/serial_base_bus.c
> > +++ b/drivers/tty/serial/serial_base_bus.c
> > @@ -99,6 +99,7 @@ void serial_base_ctrl_device_remove(struct serial_ctrl_device *ctrl_dev)
> >   		return;
> >   	device_del(&ctrl_dev->dev);
> > +	put_device(&ctrl_dev->dev);
> >   }
> >   struct serial_ctrl_device *serial_base_ctrl_add(struct uart_port *port,
> > @@ -174,6 +175,7 @@ void serial_base_port_device_remove(struct serial_port_device *port_dev)
> >   		return;
> >   	device_del(&port_dev->dev);
> > +	put_device(&port_dev->dev);
> 
> I didn't check the code, but device_unregister()?

I thought about that as it does the same, but since we're not calling
device_register() I felt it would be and unpaired call. No objections to
changing to use device_unregister() naturally if folks prefer that.

Regards,

Tony