From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Fainelli Subject: Re: [PATCH net] net: phy: Fix PHY module checks and NULL deref in phy_attach_direct() Date: Wed, 8 Feb 2017 19:07:30 -0800 Message-ID: <7a97ba93-3782-dfd0-d8eb-e528bbf39016@gmail.com> References: <20170209030526.6029-1-f.fainelli@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: maowenan , andrew@lunn.ch, rmk+kernel@armlinux.org.uk, festevam@gmail.com, davem@davemloft.net, nikita.yoush@cogentembedded.com To: netdev@vger.kernel.org Return-path: Received: from mail-qt0-f193.google.com ([209.85.216.193]:34788 "EHLO mail-qt0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751641AbdBIDOB (ORCPT ); Wed, 8 Feb 2017 22:14:01 -0500 Received: by mail-qt0-f193.google.com with SMTP id w20so25653465qtb.1 for ; Wed, 08 Feb 2017 19:14:01 -0800 (PST) In-Reply-To: <20170209030526.6029-1-f.fainelli@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: On 02/08/2017 07:05 PM, Florian Fainelli wrote: > The Generic PHY drivers gets assigned after we checked that the current > PHY driver is NULL, so we need to check a few things before we can > safely dereference d->driver. This would be causing a NULL deference to > occur when a system binds to the Generic PHY driver. Update > phy_attach_direct() to do the following: > > - grab the driver module reference after we have assigned the Generic > PHY drivers accordingly, and remember we came from the generic PHY > path > > - update the error path to clean up the module reference in case the > Generic PHY probe function fails > > - split the error path involving phy_detacht() to avoid double free/put > since phy_detach() does all the clean up > > - finally, have phy_detach() drop the module reference count before we > call device_release_driver() for the Generic PHY driver case > > Fixes: cafe8df8b9bc ("net: phy: Fix lack of reference count on PHY driver") > Signed-off-by: Florian Fainelli Just FWIW, this time I tested all error paths in phy_attach_direct() by directly injecting errors, and did that with both the Generic PHY driver and another driver to make sure there were no reference count problems, nor double frees. Thanks all! > --- > David, > > This is applicable to the "net" and the "net-next" tree since you > merged "net" into "net-next". > > I will fix the PHY driver bind/unbind mess another time, because we are running > out of time for 4.10-rc final, and it's not like it worked before and got > broken in this cycle, it just never worked (the bind/unbind). > > Thanks! > > drivers/net/phy/phy_device.c | 28 ++++++++++++++++++++-------- > 1 file changed, 20 insertions(+), 8 deletions(-) > > diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c > index 0d8f4d3847f6..8c8e15b8739d 100644 > --- a/drivers/net/phy/phy_device.c > +++ b/drivers/net/phy/phy_device.c > @@ -908,6 +908,7 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev, > struct module *ndev_owner = dev->dev.parent->driver->owner; > struct mii_bus *bus = phydev->mdio.bus; > struct device *d = &phydev->mdio.dev; > + bool using_genphy = false; > int err; > > /* For Ethernet device drivers that register their own MDIO bus, we > @@ -920,11 +921,6 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev, > return -EIO; > } > > - if (!try_module_get(d->driver->owner)) { > - dev_err(&dev->dev, "failed to get the device driver module\n"); > - return -EIO; > - } > - > get_device(d); > > /* Assume that if there is no driver, that it doesn't > @@ -938,12 +934,22 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev, > d->driver = > &genphy_driver[GENPHY_DRV_1G].mdiodrv.driver; > > + using_genphy = true; > + } > + > + if (!try_module_get(d->driver->owner)) { > + dev_err(&dev->dev, "failed to get the device driver module\n"); > + err = -EIO; > + goto error_put_device; > + } > + > + if (using_genphy) { > err = d->driver->probe(d); > if (err >= 0) > err = device_bind_driver(d); > > if (err) > - goto error; > + goto error_module_put; > } > > if (phydev->attached_dev) { > @@ -980,9 +986,14 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev, > return err; > > error: > + /* phy_detach() does all of the cleanup below */ > phy_detach(phydev); > - put_device(d); > + return err; > + > +error_module_put: > module_put(d->driver->owner); > +error_put_device: > + put_device(d); > if (ndev_owner != bus->owner) > module_put(bus->owner); > return err; > @@ -1045,6 +1056,8 @@ void phy_detach(struct phy_device *phydev) > > phy_led_triggers_unregister(phydev); > > + module_put(phydev->mdio.dev.driver->owner); > + > /* If the device had no specific driver before (i.e. - it > * was using the generic driver), we unbind the device > * from the generic driver so that there's a chance a > @@ -1065,7 +1078,6 @@ void phy_detach(struct phy_device *phydev) > bus = phydev->mdio.bus; > > put_device(&phydev->mdio.dev); > - module_put(phydev->mdio.dev.driver->owner); > if (ndev_owner != bus->owner) > module_put(bus->owner); > } > -- Florian