Re: [PATCH v5] of/pci: Fix memory leak in of_pci_get_host_bridge_resources

[jeffy <jeffy.chen@rock-chips.com>]

Hi Bjorn,

On 05/18/2017 05:08 AM, Bjorn Helgaas wrote:
> On Wed, Apr 05, 2017 at 10:28:22AM +0800, Jeffy Chen wrote:
>> Currently we only free the allocated resource struct when error.
>> This would cause memory leak after pci_free_resource_list.
>
> I think I see the problem here.  The release path is this:
>
>    pci_release_host_bridge_dev
>      pci_free_resource_list
>        resource_list_free
> 	list_for_each_entry_safe(entry, tmp, head, node)
> 	  resource_list_destroy_entry
> 	    resource_list_del
> 	    resource_list_free_entry
> 	      kfree(entry)
>
> but that frees only the struct resource_entry, not the struct resource
> pointed to by entry->res.  Is that right?
right, that's the leak.

>
> And this patch solves it for of_pci_get_host_bridge_resources() by
> always making entry->res point to entry->__res, which is an element in
> struct resource_entry, so it's sufficient to free the resource_entry.
>
> The memory management here is pretty tangled.  I wonder if there's
> some way to simplify it so it's easier to make sure everybody does it
> correctly.  For example, could we remove the entry->res pointer
> completely and force everybody to use entry->__res?
i've tried something like this in 
https://patchwork.kernel.org/patch/9638003/

but it turns out there are a few codes trying to use shared 
resources(entry->res pointer point to some common resources), for example:

./arch/tile/kernel/pci.c:307: 
pci_add_resource(&resources, &ioport_resource);
./arch/tile/kernel/pci.c:308: 
pci_add_resource(&resources, &iomem_resource);

so i tried to use IORESOURCE_AUTO to handle non-common(private) resources.


and i saw drivers/pnp/manager.c tried to handle something like this too, 
by manually free resources marked as IORESOURCE_AUTO:
static void pnp_clean_resource_table(struct pnp_dev *dev)
{
         struct pnp_resource *pnp_res, *tmp;

         list_for_each_entry_safe(pnp_res, tmp, &dev->resources, list) {
                 if (pnp_res->res.flags & IORESOURCE_AUTO)
                         pnp_free_resource(pnp_res);
         }
}


>
>> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
>> ---
>>
>> Changes in v5:
>> Fix some careless compile errors.
>>
>> Changes in v4:
>> Use IORESOURCE_AUTO to mark struct resources which could be copied.
>>
>> Changes in v3:
>> Add some comments.
>>
>> Changes in v2:
>> Don't change the resource_list_create_entry's behavior.
>>
>>   drivers/of/of_pci.c | 51 ++++++++++++++++++---------------------------------
>>   drivers/pci/bus.c   |  7 ++++++-
>>   2 files changed, 24 insertions(+), 34 deletions(-)
>>
>> diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
>> index 0ee42c3..49233bf 100644
>> --- a/drivers/of/of_pci.c
>> +++ b/drivers/of/of_pci.c
>> @@ -189,9 +189,7 @@ int of_pci_get_host_bridge_resources(struct device_node *dev,
>>   			unsigned char busno, unsigned char bus_max,
>>   			struct list_head *resources, resource_size_t *io_base)
>>   {
>> -	struct resource_entry *window;
>> -	struct resource *res;
>> -	struct resource *bus_range;
>> +	struct resource res;
>>   	struct of_pci_range range;
>>   	struct of_pci_range_parser parser;
>>   	char range_type[4];
>> @@ -200,24 +198,21 @@ int of_pci_get_host_bridge_resources(struct device_node *dev,
>>   	if (io_base)
>>   		*io_base = (resource_size_t)OF_BAD_ADDR;
>>
>> -	bus_range = kzalloc(sizeof(*bus_range), GFP_KERNEL);
>> -	if (!bus_range)
>> -		return -ENOMEM;
>> -
>>   	pr_info("host bridge %s ranges:\n", dev->full_name);
>>
>> -	err = of_pci_parse_bus_range(dev, bus_range);
>> +	err = of_pci_parse_bus_range(dev, &res);
>>   	if (err) {
>> -		bus_range->start = busno;
>> -		bus_range->end = bus_max;
>> -		bus_range->flags = IORESOURCE_BUS;
>> -		pr_info("  No bus range found for %s, using %pR\n",
>> -			dev->full_name, bus_range);
>> +		res.start = busno;
>> +		res.end = bus_max;
>> +		res.flags = IORESOURCE_BUS;
>> +		pr_info("  No bus range found for %s\n", dev->full_name);
>>   	} else {
>> -		if (bus_range->end > bus_range->start + bus_max)
>> -			bus_range->end = bus_range->start + bus_max;
>> +		if (res.end > res.start + bus_max)
>> +			res.end = res.start + bus_max;
>>   	}
>> -	pci_add_resource(resources, bus_range);
>> +
>> +	res.flags |= IORESOURCE_AUTO;
>> +	pci_add_resource(resources, &res);
>>
>>   	/* Check for ranges property */
>>   	err = of_pci_range_parser_init(&parser, dev);
>> @@ -244,24 +239,16 @@ int of_pci_get_host_bridge_resources(struct device_node *dev,
>>   		if (range.cpu_addr == OF_BAD_ADDR || range.size == 0)
>>   			continue;
>>
>> -		res = kzalloc(sizeof(struct resource), GFP_KERNEL);
>> -		if (!res) {
>> -			err = -ENOMEM;
>> -			goto parse_failed;
>> -		}
>> -
>> -		err = of_pci_range_to_resource(&range, dev, res);
>> -		if (err) {
>> -			kfree(res);
>> +		err = of_pci_range_to_resource(&range, dev, &res);
>> +		if (err)
>>   			continue;
>> -		}
>>
>> -		if (resource_type(res) == IORESOURCE_IO) {
>> +		if (resource_type(&res) == IORESOURCE_IO) {
>>   			if (!io_base) {
>>   				pr_err("I/O range found for %s. Please provide an io_base pointer to save CPU base address\n",
>>   					dev->full_name);
>>   				err = -EINVAL;
>> -				goto conversion_failed;
>> +				goto parse_failed;
>>   			}
>>   			if (*io_base != (resource_size_t)OF_BAD_ADDR)
>>   				pr_warn("More than one I/O resource converted for %s. CPU base address for old range lost!\n",
>> @@ -269,16 +256,14 @@ int of_pci_get_host_bridge_resources(struct device_node *dev,
>>   			*io_base = range.cpu_addr;
>>   		}
>>
>> -		pci_add_resource_offset(resources, res,	res->start - range.pci_addr);
>> +		res.flags |= IORESOURCE_AUTO;
>> +		pci_add_resource_offset(resources, &res,
>> +					res.start - range.pci_addr);
>>   	}
>>
>>   	return 0;
>>
>> -conversion_failed:
>> -	kfree(res);
>>   parse_failed:
>> -	resource_list_for_each_entry(window, resources)
>> -		kfree(window->res);
>>   	pci_free_resource_list(resources);
>>   	return err;
>>   }
>> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
>> index bc56cf1..3dbcb95 100644
>> --- a/drivers/pci/bus.c
>> +++ b/drivers/pci/bus.c
>> @@ -22,12 +22,17 @@ void pci_add_resource_offset(struct list_head *resources, struct resource *res,
>>   {
>>   	struct resource_entry *entry;
>>
>> -	entry = resource_list_create_entry(res, 0);
>> +	entry = resource_list_create_entry(NULL, 0);
>
> If we make this change, there are no callers of
> resource_list_create_entry() that supply a non-NULL "res", so
> we could remove that argument completely.
>
>>   	if (!entry) {
>>   		printk(KERN_ERR "PCI: can't add host bridge window %pR\n", res);
>>   		return;
>>   	}
>>
>> +	if (res->flags & IORESOURCE_AUTO)
>> +		*entry->res = *res;
>> +	else
>> +		entry->res = res;
>> +
>>   	entry->offset = offset;
>>   	resource_list_add_tail(entry, resources);
>>   }
>> --
>> 2.1.4
>>
>>
>
>
>