netdev - Re: [PATCHi v2] net: mdiobus: fix device unregistering in mdiobus

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Date:   Fri, 28 Aug 2020 16:15:12 +0200
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>, kernel@...gutronix.de
Subject: Re: [PATCHi v2] net: mdiobus: fix device unregistering in
 mdiobus_register

On Thu, Aug 27, 2020 at 10:48:48AM +0200, Heiner Kallweit wrote:
> On 27.08.2020 09:06, Sascha Hauer wrote:
> > After device_register has been called the device structure may not be
> > freed anymore, put_device() has to be called instead. This gets violated
> > when device_register() or any of the following steps before the mdio
> > bus is fully registered fails. In this case the caller will call
> > mdiobus_free() which then directly frees the mdio bus structure.
> > 
> > Set bus->state to MDIOBUS_UNREGISTERED right before calling
> > device_register(). With this mdiobus_free() calls put_device() instead
> > as it ought to be.
> > 
> > Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
> > ---
> > 
> > Changes since v1:
> > - set bus->state before calling device_register(), not afterwards
> > 
> >  drivers/net/phy/mdio_bus.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
> > index 0af20faad69d..9434b04a11c8 100644
> > --- a/drivers/net/phy/mdio_bus.c
> > +++ b/drivers/net/phy/mdio_bus.c
> > @@ -534,6 +534,8 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
> >  	bus->dev.groups = NULL;
> >  	dev_set_name(&bus->dev, "%s", bus->id);
> >  
> > +	bus->state = MDIOBUS_UNREGISTERED;
> > +
> >  	err = device_register(&bus->dev);
> >  	if (err) {
> >  		pr_err("mii_bus %s failed to register\n", bus->id);
> > 
> LGTM. Just two points:
> 1. Subject has a typo (PATCHi). And it should be [PATCH net v2], because it's
>    something for the stable branch.
> 2. A "Fixes" tag is needed.

Uh, AFAICT this fixes a patch from 2008, this makes for quite some
stable updates :)

Sascha

| commit 161c8d2f50109b44b664eaf23831ea1587979a61
| Author: Krzysztof Halasa <khc@...waw.pl>
| Date:   Thu Dec 25 16:50:41 2008 -0800
| 
|     net: PHYLIB mdio fixes #2

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