Re: [PATCH v2 2/2] of/pci: Fix memory leak in of_pci_get_host_bridge_resources

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Hi Rob & Dmitry,

On 03/24/2017 06:58 AM, Dmitry Torokhov wrote:
On Thu, Mar 23, 2017 at 3:07 PM, Rob Herring <robh@xxxxxxxxxx> wrote:
On Thu, Mar 23, 2017 at 3:12 AM, Jeffy Chen <jeffy.chen@xxxxxxxxxxxxxx> wrote:
Currently we only free the allocated resource struct when error.
This would cause memory leak after pci_free_resource_list.

Signed-off-by: Jeffy Chen <jeffy.chen@xxxxxxxxxxxxxx>
---

Changes in v2:
Don't change the resource_list_create_entry's behavior.

  drivers/of/of_pci.c | 57 +++++++++++++++++++++++------------------------------
  1 file changed, 25 insertions(+), 32 deletions(-)

diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
index 0ee42c3..a0ec246 100644
--- a/drivers/of/of_pci.c
+++ b/drivers/of/of_pci.c
@@ -190,8 +190,7 @@ int of_pci_get_host_bridge_resources(struct device_node *dev,
                         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 +199,24 @@ 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;
+       }
+       window = pci_add_resource(resources, NULL);
+       if (!window) {
+               err = -ENOMEM;
+               goto parse_failed;
         }
-       pci_add_resource(resources, bus_range);
+       *window->res = res;

Well, now this seems racy. You add a blank resource to the list first
and then fill it in.


Huh? There is absolutely no guarantees for concurrent access here.
pcI_add_resource_offset() first adds a resource and then modifies
offset. Here we add an empty resource and then fill it in.
currently, we are using of_pci_get_host_bridge_resources in this pattern:

create resource list:
        LIST_HEAD(res);
...
add resources into the list:
        err = of_pci_get_host_bridge_resources(dev->of_node, 0, 0xff,
                                               &res, &io_base);
...
walk over the list:
        /* Get the I/O and memory ranges from DT */
        resource_list_for_each_entry(win, &res) {

so only of_pci_get_host_bridge_resources is accessing this list at that time.

and an empty resource is harmless i think(with zero size and flags) ;)

maybe i should add some comments in the patch


Thanks.



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