On Wed, Nov 16, 2016 at 09:06:26AM -0800, Florian Fainelli wrote:
> On 11/16/2016 06:47 AM, Johan Hovold wrote:
> > Make sure to drop the reference taken by of_phy_find_device() when
> > registering and deregistering the fixed-link PHY-device.
> >
> > Note that we need to put both references held at deregistration.
> >
> > Fixes: 39b0c705195e ("net: dsa: Allow configuration of CPU & DSA port
> > speeds/duplex")
> > Signed-off-by: Johan Hovold <jo...@kernel.org>
> > ---
> >
> > Hi,
> >
> > This is one has been compile tested only, but fixes a couple of leaks
> > similar to one that was found in the cpsw driver for which I just posted
> > a patch.
> >
> > It turns out all drivers but DSA fail to deregister the fixed-link PHYs
> > registered by of_phy_register_fixed_link(). Due to the way this
> > interface was designed, deregistering such a PHY is a bit cumbersome and
> > looks like it would benefit from a common helper.
> >
> > However, perhaps the interface should instead be changed so that the PHY
> > device is returned so that drivers do not need to use
> > of_phy_find_device() when they need to access properties of the fixed
> > link (e.g. as in dsu_cpu_dsa_setup below).
> >
> > Thoughts?
> >
> > Thanks,
> > Johan
> >
> >
> > net/dsa/dsa.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
> > index a6902c1e2f28..798a6a776a5f 100644
> > --- a/net/dsa/dsa.c
> > +++ b/net/dsa/dsa.c
> > @@ -233,6 +233,8 @@ int dsa_cpu_dsa_setup(struct dsa_switch *ds, struct
> > device *dev,
> > genphy_read_status(phydev);
> > if (ds->ops->adjust_link)
> > ds->ops->adjust_link(ds, port, phydev);
> > +
> > + phy_device_free(phydev); /* of_phy_find_device */
> > }
> >
> > return 0;
> > @@ -509,8 +511,12 @@ void dsa_cpu_dsa_destroy(struct device_node *port_dn)
> > if (of_phy_is_fixed_link(port_dn)) {
> > phydev = of_phy_find_device(port_dn);
> > if (phydev) {
> > - phy_device_free(phydev);
> > fixed_phy_unregister(phydev);
> > + /* Put references taken by of_phy_find_device() and
> > + * of_phy_register_fixed_link().
> > + */
> > + phy_device_free(phydev);
> > + phy_device_free(phydev);
>
> Double free, this looks bogus here. Actually would not this mean a
> triple free since you already free in dsa_cpu_dsa_setup() which is
> paired with dsa_cpu_dsa_destroy()?
The naming of phy_device_free() is unfortunate when it's really a put():
void phy_device_free(struct phy_device *phydev)
{
put_device(&phydev->mdio.dev);
}
which may need to be called multiple times, specifically after a call to
of_phy_find_device() which takes another reference.
With this patch the refcounts are properly balanced.
Johan
