linux-kernel - Re: [PATCH] PCI: keystone: fix interrupt-controller-node lookup

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Date:   Tue, 14 Nov 2017 18:34:37 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     Johan Hovold <johan@...nel.org>,
        Murali Karicheri <m-karicheri2@...com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org>
Subject: Re: [PATCH] PCI: keystone: fix interrupt-controller-node lookup

On Mon, Nov 13, 2017 at 10:43:06AM +0000, Lorenzo Pieralisi wrote:
> Hi Johan,
> 
> On Sun, Nov 12, 2017 at 01:28:50PM +0100, Johan Hovold wrote:
> > Fix child-node lookup during initialisation, which ended up searching
> > the whole device tree depth-first starting at the parent rather than
> > just matching on its children.
> > 
> > To make things worse, the parent pci node was prematurely freed, while
> > the child interrupt-controller node was leaked.
> 
> Thanks for fixing this. I would kindly ask you please to split the
> patch in two since there are two bugs you are fixing at once.

I guess it depends on how you look at it. I'm fixing the child-node
lookup which just happens to broken in several ways: tree-wide search,
parent-node put-imbalance and node leaks in both the error and
success paths.

Fixing that in two or even three patches seems a bit excessive,
especially as the first patch would in a sense be broken as the
of_get_child_by_name() does indeed (also) return a refcounted node. And
furthermore, this broken lookup, in all of its aspects, was introduced
by a single commit.

But if you insist, I'll split it up of course.

Thanks,
Johan

> > Fixes: 0c4ffcfe1fbc ("PCI: keystone: Add TI Keystone PCIe driver")
> > Cc: stable <stable@...r.kernel.org>     # 3.18
> > Cc: Murali Karicheri <m-karicheri2@...com>
> > ---
> >  drivers/pci/dwc/pci-keystone.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/dwc/pci-keystone.c b/drivers/pci/dwc/pci-keystone.c
> > index 5bee3af47588..39405598b22d 100644
> > --- a/drivers/pci/dwc/pci-keystone.c
> > +++ b/drivers/pci/dwc/pci-keystone.c
> > @@ -178,7 +178,7 @@ static int ks_pcie_get_irq_controller_info(struct keystone_pcie *ks_pcie,
> >  	}
> >  
> >  	/* interrupt controller is in a child node */
> > -	*np_temp = of_find_node_by_name(np_pcie, controller);
> > +	*np_temp = of_get_child_by_name(np_pcie, controller);
> >  	if (!(*np_temp)) {
> >  		dev_err(dev, "Node for %s is absent\n", controller);
> >  		return -EINVAL;
> > @@ -187,6 +187,7 @@ static int ks_pcie_get_irq_controller_info(struct keystone_pcie *ks_pcie,
> >  	temp = of_irq_count(*np_temp);
> >  	if (!temp) {
> >  		dev_err(dev, "No IRQ entries in %s\n", controller);
> > +		of_node_put(*np_temp);
> >  		return -EINVAL;
> >  	}
> >  
> > @@ -204,6 +205,8 @@ static int ks_pcie_get_irq_controller_info(struct keystone_pcie *ks_pcie,
> >  			break;
> >  	}
> >  
> > +	of_node_put(*np_temp);
> > +
> >  	if (temp) {
> >  		*num_irqs = temp;
> >  		return 0;
> > -- 
> > 2.15.0
> >