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

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Date:   Wed, 22 Mar 2017 09:39:02 -0500
From:   Rob Herring <robh@...nel.org>
To:     Jeffy Chen <jeffy.chen@...k-chips.com>
Cc:     "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 2/2] of/pci: Fix memory leak in of_pci_get_host_bridge_resources

On Tue, Mar 21, 2017 at 9:25 PM, 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>
> ---
>
>  drivers/of/of_pci.c | 48 +++++++++++++++---------------------------------
>  1 file changed, 15 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
> index 0ee42c3..269393bc 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 +198,19 @@ 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);
> +       pci_add_resource(resources, &res);

You are passing a stack variable to pci_add_resource and it doesn't
make a copy of it. I assume the resource needs to live after you exit
this function.

If we have a leak, can't you just add a free in the correct spot? That
would be a lot easier to review.

Rob