linux-kernel - Re: [PATCH v2 2/2] of/pci: Fix memory leak in of_pci_get_host_bridge

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Date:   Thu, 23 Mar 2017 15:58:56 -0700
From:   Dmitry Torokhov <dtor@...omium.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Jeffy Chen <jeffy.chen@...k-chips.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        toshi.kani@....com, Shawn Lin <shawn.lin@...k-chips.com>,
        Brian Norris <briannorris@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        Dmitry Torokhov <dtor@...omium.org>,
        Frank Rowand <frowand.list@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] of/pci: Fix memory leak in of_pci_get_host_bridge_resources

On Thu, Mar 23, 2017 at 3:07 PM, Rob Herring <robh@...nel.org> wrote:
> On Thu, Mar 23, 2017 at 3:12 AM, Jeffy Chen <jeffy.chen@...k-chips.com> 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@...k-chips.com>
>> ---
>>
>> 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.

Thanks.

-- 
Dmitry