From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johan Hovold Subject: Re: [PATCH 6/7] thermal: max77620: fix device-node reference imbalance Date: Wed, 31 May 2017 10:28:27 +0200 Message-ID: <20170531082827.GC6735@localhost> References: <20170530162554.26159-1-johan@kernel.org> <20170530162554.26159-7-johan@kernel.org> <41a7b947-579f-e9ba-188d-699e7ff0b27d@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <41a7b947-579f-e9ba-188d-699e7ff0b27d@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: Tyrel Datwyler Cc: Johan Hovold , Greg Kroah-Hartman , Linus Walleij , Peter Chen , Rob Herring , Arnd Bergmann , Sricharan R , Zhang Rui , Eduardo Valentin , linux-pm@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable , Laxman Dewangan List-Id: linux-pm@vger.kernel.org On Tue, May 30, 2017 at 03:59:10PM -0700, Tyrel Datwyler wrote: > On 05/30/2017 09:25 AM, Johan Hovold wrote: > > The thermal child device reuses the parent MFD-device device-tree node > > when registering a thermal zone, but did not take a reference to the > > node. > > > > This leads to a reference imbalance, and potential use-after-free, when > > the node reference is dropped by the platform-bus device destructor > > (once for the child and later again for the parent). > > > > Fix this by dropping any reference already held to a device-tree node > > and getting a reference to the parent's node which will be balanced on > > reprobe or on platform-device release, whichever comes first. > > > > Note that simply clearing the of_node pointer on probe errors and on > > driver unbind would not allow the use of device-managed resources as > > specifically thermal_zone_of_sensor_unregister() claims that a valid > > device-tree node pointer is needed during deregistration (even if it > > currently does not seem to use it). > > > > Fixes: ec4664b3fd6d ("thermal: max77620: Add thermal driver for reporting junction temp") > > Cc: stable # 4.9 > > Cc: Laxman Dewangan > > Signed-off-by: Johan Hovold > > --- > > drivers/thermal/max77620_thermal.c | 10 ++++++++-- > > 1 file changed, 8 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/thermal/max77620_thermal.c b/drivers/thermal/max77620_thermal.c > > index e9a1fe342760..71d35f3c9215 100644 > > --- a/drivers/thermal/max77620_thermal.c > > +++ b/drivers/thermal/max77620_thermal.c > > @@ -104,8 +104,6 @@ static int max77620_thermal_probe(struct platform_device *pdev) > > return -EINVAL; > > } > > > > - pdev->dev.of_node = pdev->dev.parent->of_node; > > - > > mtherm->dev = &pdev->dev; > > mtherm->rmap = dev_get_regmap(pdev->dev.parent, NULL); > > if (!mtherm->rmap) { > > @@ -113,6 +111,14 @@ static int max77620_thermal_probe(struct platform_device *pdev) > > return -ENODEV; > > } > > > > + /* > > + * Drop any current reference to a device-tree node and get a > > + * reference to the parent's node which will be balanced on reprobe or > > + * on platform-device release. > > + */ > > + of_node_put(pdev->dev.of_node); > > + pdev->dev.of_node = of_node_get(pdev->dev.parent->of_node); > > + > > This seems like needless churn. Can't this just be squashed into patch > #7? As I just replied to Eduardo, I'm fixing two separate issues here of which this one might qualify for stable while the other (7/7) does not. Thanks, Johan