linux-kernel - Re: [PATCH] PCI: endpoint: handle probable NULL pointer access

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Date:   Wed, 25 Oct 2017 17:32:07 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        Pankaj Dubey <pankaj.dubey@...sung.com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH] PCI: endpoint: handle probable NULL pointer access

Hi,

On Wednesday 25 October 2017 01:32 AM, Bjorn Helgaas wrote:
> On Thu, Oct 12, 2017 at 09:27:57AM +0530, Pankaj Dubey wrote:
>> controller_group allocation in pci_ep_cfs_init function can fail
>> so we should have a check while using it in pci_ep_cfs_add_epc_group
>> for registering group, else we will hit NULL pointer access.
>>
>> This patch adds required check for the same and returns -EPROBE_DEFER,
>> so that endpoint controller driver probe can be reattempted later
>> in case controller_group is not allocated because pci_ep_cfs_init is
>> not yet called.
>>
>> Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>
> 
> Looking for Kishon's ack here.
> 
>> ---
>>  drivers/pci/endpoint/pci-ep-cfs.c   | 7 ++++++-
>>  drivers/pci/endpoint/pci-epc-core.c | 4 ++++
>>  2 files changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/pci/endpoint/pci-ep-cfs.c b/drivers/pci/endpoint/pci-ep-cfs.c
>> index 424fdd6..3cac818 100644
>> --- a/drivers/pci/endpoint/pci-ep-cfs.c
>> +++ b/drivers/pci/endpoint/pci-ep-cfs.c
>> @@ -172,7 +172,12 @@ struct config_group *pci_ep_cfs_add_epc_group(const char *name)
>>  	group = &epc_group->group;
>>  
>>  	config_group_init_type_name(group, name, &pci_epc_type);
>> -	ret = configfs_register_group(controllers_group, group);
>> +
>> +	if (controllers_group)
>> +		ret = configfs_register_group(controllers_group, group);
>> +	else
>> +		ret = -EPROBE_DEFER;
>> +

Do you ever face this issue? Ideally controllers_group should always be
initialized if the dependencies are modeled properly.
>>  	if (ret) {
>>  		pr_err("failed to register configfs group for %s\n", name);
>>  		goto err_register_group;
>> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
>> index 42c2a11..d327a2a 100644
>> --- a/drivers/pci/endpoint/pci-epc-core.c
>> +++ b/drivers/pci/endpoint/pci-epc-core.c
>> @@ -518,6 +518,10 @@ __pci_epc_create(struct device *dev, const struct pci_epc_ops *ops,
>>  		goto put_dev;
>>  
>>  	epc->group = pci_ep_cfs_add_epc_group(dev_name(dev));
>> +	if (IS_ERR(epc->group)) {
>> +		ret = -EPROBE_DEFER;

should use the return value of pci_ep_cfs_add_epc_group().

However I don't think this is required since drivers might not actually need cfs.

Thanks
Kishon