linux-kernel - Re: [PATCH] PCI: kirin: Fix of_node

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Date:   Fri, 5 Nov 2021 09:52:44 +0800
From:   Jiabing Wan <wanjiabing@...o.com>
To:     Rob Herring <robh@...nel.org>, Bjorn Helgaas <helgaas@...nel.org>
Cc:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Xiaowei Song <songxiaowei@...ilicon.com>,
        Binghui Wang <wangbinghui@...ilicon.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        PCI <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        jiabing.wan@...com
Subject: Re: [PATCH] PCI: kirin: Fix of_node_put() issue in pcie-kirin



On 2021/11/4 21:56, Rob Herring wrote:
> On Wed, Nov 3, 2021 at 9:31 AM Bjorn Helgaas <helgaas@...nel.org> wrote:
>> [+to Mauro, author of code being changed,
>> Rob for "of_pci_get_devfn()" naming question]
>>
>> On Wed, Nov 03, 2021 at 02:25:18AM -0400, Wan Jiabing wrote:
>>> Fix following coccicheck warning:
>>> ./drivers/pci/controller/dwc/pcie-kirin.c:414:2-34: WARNING: Function
>>> for_each_available_child_of_node should have of_node_put() before return.
>>>
>>> Early exits from for_each_available_child_of_node should decrement the
>>> node reference counter. Replace return by goto here.
>>>
>>> Signed-off-by: Wan Jiabing <wanjiabing@...o.com>
>>> ---
>>>   drivers/pci/controller/dwc/pcie-kirin.c | 3 ++-
>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/pci/controller/dwc/pcie-kirin.c b/drivers/pci/controller/dwc/pcie-kirin.c
>>> index 06017e826832..23a2c076ce53 100644
>>> --- a/drivers/pci/controller/dwc/pcie-kirin.c
>>> +++ b/drivers/pci/controller/dwc/pcie-kirin.c
>>> @@ -422,7 +422,8 @@ static int kirin_pcie_parse_port(struct kirin_pcie *pcie,
>>>                        pcie->num_slots++;
>>>                        if (pcie->num_slots > MAX_PCI_SLOTS) {
>>>                                dev_err(dev, "Too many PCI slots!\n");
>>> -                             return -EINVAL;
>>> +                             ret = -EINVAL;
>>> +                             goto put_node;
>>>                        }
>>>
>>>                        ret = of_pci_get_devfn(child);
>> This is a change to the code added here:
>>    https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/commit/?id=31bd24f0cfe0
>>
>> This fix looks right to me; all the other early exits from the inner
>> loop drop the "child" reference.
>>
>> But this is a nested loop and the *outer* loop also increments
>> refcounts, and I don't see that outer loop reference on "parent" being
>> dropped at all:
>>
>>      for_each_available_child_of_node(node, parent) {
>>        for_each_available_child_of_node(parent, child) {
>>          ...
>>          if (error)
>>            goto put_node;
>>        }
>>      }
>>
>>    put_node:
>>      of_node_put(child);
> Indeed. There should be a put on the parent.
OK, I'll fix in v2. Thanks.

Jiabing Wan