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

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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@xxxxxxxxxxxxxx>
---

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







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