On Wed, Mar 09, 2022 at 12:25:03PM +0100, Greg Kroah-Hartman wrote:
> On Wed, Mar 09, 2022 at 11:10:33AM +0000, Miaoqian Lin wrote:
> > The device_node pointer is returned by of_parse_phandle() with refcount
> > incremented. We should use of_node_put() on it when done.
> >
> > Fixes: 8934d3e4d0e7 ("usb: musb: omap2430: Don't use omap_get_control_dev()")
> > Signed-off-by: Miaoqian Lin <linmq006@xxxxxxxxx>
> > ---
> > drivers/usb/musb/omap2430.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/usb/musb/omap2430.c b/drivers/usb/musb/omap2430.c
> > index 7d4d0713f4f0..4a963cfa385b 100644
> > --- a/drivers/usb/musb/omap2430.c
> > +++ b/drivers/usb/musb/omap2430.c
> > @@ -363,6 +363,7 @@ static int omap2430_probe(struct platform_device *pdev)
> > control_node = of_parse_phandle(np, "ctrl-module", 0);
> > if (control_node) {
> > control_pdev = of_find_device_by_node(control_node);
> > + of_node_put(control_node);
> > if (!control_pdev) {
> > dev_err(&pdev->dev, "Failed to get control device\n");
> > ret = -EINVAL;
> > --
> > 2.17.1
> >
>
> How was this tested?
Hi, Greg Kroah-Hartman
I mainly went through the specifications of of_parse_phandle() and
of_find_device_by_node(), and checked their usages in the codebase
to infer their correct usages then found out the deviant one, and
manually confirmed it.
In doc of of_parse_phandle() it mentions :
> Return: The device_node pointer with refcount incremented. Use
> * of_node_put() on it when done.
In the doc of and of_find_device_by_node() it mentions:
> * Takes a reference to the embedded struct device which needs to
> be dropped
> * after use.
In this case, control_node is a local variable, and it never be used
after of_find_device_by_node(), of_find_device_by_node() call will
take its own reference. So the reference holded by control_node
should be released.
I checked the usages
pattern——`$ret=of_parse_phandle();of_find_device_by_node($ret);` in
codebase and most of them handle the reference after use.
For example:
- function pwm_omap_dmtimer_probe in drivers/pwm/pwm-omap-dmtimer.c
- function mtk_smi_device_link_common in drivers/memory/mtk-smi.c,
- function devm_tegra_memory_controller_get in
drivers/memory/tegra/mc.c.
I also took similar bugfixes for reference, for exmaple:
- commit c8d0ccfd73da ("media: mtk-vpu: fix leaked of_node references")
- commit 3d38faef0de1 ("ath11k: add missing of_node_put() to avoid leak")
So I sent patch for this one. Still not sure if it's correct,
I hope the developers could double check this, Thanks.
