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

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  Re: [PATCH v2 2/2] of/pci: Fix memory leak in of_pci_get_host_bridge_resources Bjorn Helgaas <bhelgaas@google.com> - 2017-04-04 21:20 +0200
    Re: [PATCH v2 2/2] of/pci: Fix memory leak in of_pci_get_host_bridge_resources jeffy <jeffy.chen@rock-chips.com> - 2017-04-05 04:30 +0200
      Re: [PATCH v2 2/2] of/pci: Fix memory leak in of_pci_get_host_bridge_resources Rob Herring <robh@kernel.org> - 2017-04-05 15:30 +0200

#1616349 — Re: [PATCH v2 2/2] of/pci: Fix memory leak in of_pci_get_host_bridge_resources

On Thu, Mar 23, 2017 at 5:58 PM, Dmitry Torokhov <dtor@chromium.org> wrote:
> On Thu, Mar 23, 2017 at 3:07 PM, Rob Herring <robh@kernel.org> wrote:
>> On Thu, Mar 23, 2017 at 3:12 AM, Jeffy Chen <jeffy.chen@rock-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@rock-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.

I don't really like this pattern either.  Even if there's no actual
racy behavior, it takes more analysis than necessary to figure that
out.

pci_add_resource_offset() allocates a resource list entry, sets the
offset, then adds it to the list.  It doesn't update a resource entry
that might be visible to anybody else.  Here we do update a resource
that is already visible to others because it's already on the list.

Bjorn

BTW, please CC linux-pci on the entire series so it's easier to
review.  I don't know where you envision having this applied, but I
only apply things to the PCI tree after they appear on linux-pci.

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#1616530

Hi Bjorn,

On 04/05/2017 03:18 AM, Bjorn Helgaas wrote:
> On Thu, Mar 23, 2017 at 5:58 PM, Dmitry Torokhov <dtor@chromium.org> wrote:
>> On Thu, Mar 23, 2017 at 3:07 PM, Rob Herring <robh@kernel.org> wrote:
>>> On Thu, Mar 23, 2017 at 3:12 AM, Jeffy Chen <jeffy.chen@rock-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@rock-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.
>
> I don't really like this pattern either.  Even if there's no actual
> racy behavior, it takes more analysis than necessary to figure that
> out.
>
> pci_add_resource_offset() allocates a resource list entry, sets the
> offset, then adds it to the list.  It doesn't update a resource entry
> that might be visible to anybody else.  Here we do update a resource
> that is already visible to others because it's already on the list.
i was following ./drivers/pnp/resource.c, but i'm agree this is not a 
good way.

i'll upload a new version to fix this in another way. more ideas:
1/ pass a struct device to of_pci_get_host_bridge_resources and use 
devm_kzalloc
2/ add a new type of flags(or reuse IORESOURCE_AUTO) to tell 
pci_free_resource_list to kfree them)
3/ add new helpers of of_pci_add_resource[_offset] to alloc empty res, 
fill it, add to list.
>
> Bjorn
>
> BTW, please CC linux-pci on the entire series so it's easier to
> review.  I don't know where you envision having this applied, but I
> only apply things to the PCI tree after they appear on linux-pci.
>
oh, sorry, didn't notice that, will do in next version.
>
>

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#1616922

On Tue, Apr 4, 2017 at 9:22 PM, jeffy <jeffy.chen@rock-chips.com> wrote:
> Hi Bjorn,
>
>
> On 04/05/2017 03:18 AM, Bjorn Helgaas wrote:
>>
>> On Thu, Mar 23, 2017 at 5:58 PM, Dmitry Torokhov <dtor@chromium.org>
>> wrote:
>>>
>>> On Thu, Mar 23, 2017 at 3:07 PM, Rob Herring <robh@kernel.org> wrote:
>>>>
>>>> On Thu, Mar 23, 2017 at 3:12 AM, Jeffy Chen <jeffy.chen@rock-chips.com>
>>>> wrote:
>>>>>
>>>>> Currently we only free the allocated resource struct when error.
>>>>> This would cause memory leak after pci_free_resource_list.

>>>>> -       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.
>>
>>
>> I don't really like this pattern either.  Even if there's no actual
>> racy behavior, it takes more analysis than necessary to figure that
>> out.
>>
>> pci_add_resource_offset() allocates a resource list entry, sets the
>> offset, then adds it to the list.  It doesn't update a resource entry
>> that might be visible to anybody else.  Here we do update a resource
>> that is already visible to others because it's already on the list.
>
> i was following ./drivers/pnp/resource.c, but i'm agree this is not a good
> way.
>
> i'll upload a new version to fix this in another way. more ideas:
> 1/ pass a struct device to of_pci_get_host_bridge_resources and use
> devm_kzalloc

I would pick this one of the 3 options or...

> 2/ add a new type of flags(or reuse IORESOURCE_AUTO) to tell
> pci_free_resource_list to kfree them)
> 3/ add new helpers of of_pci_add_resource[_offset] to alloc empty res, fill
> it, add to list.

2 other options:

Add a function to undo everything that
of_pci_get_host_bridge_resources does. Then every caller of
of_pci_get_host_bridge_resources should have a call to that function.

Or maybe you can add a pci_free_resource_list_and_resources (needs a
better name) to free both resources and list. Then audit all the
current callers of pci_free_resource_list and determine which one's
can be changed (maybe it is all of them).

Rob

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