linux-kernel - Re: linux-next: dock_link

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Date:	Sat, 18 Feb 2012 21:37:18 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	Holger Macht <holger@...ac.de>
Cc:	Hugh Dickins <hughd@...gle.com>, Matthew Garrett <mjg@...hat.com>,
	Jeff Garzik <jgarzik@...hat.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: linux-next: dock_link_device is oopsy

On Sat, Feb 18, 2012 at 9:26 PM, Holger Macht <holger@...ac.de> wrote:
> On Sa 18. Feb - 21:05:18, Hillf Danton wrote:
>> On Sat, Feb 18, 2012 at 7:14 PM, Holger Macht <holger@...ac.de> wrote:
>> > So how about that?
>> >
>> > acpi: Bail out when linking devices and there are no dock stations
>> >
>> > If dock_station_count is zero, we allocate zero memory and don't check
>> > this at future references. So bail out if there are actually no dock
>> > stations.
>> >
>> > Signed-off-by: Holger Macht <holger@...ac.de>
>> > ---
>> >  drivers/acpi/dock.c |   19 ++++++++++++++-----
>> >  1 files changed, 14 insertions(+), 5 deletions(-)
>> >
>> > diff --git a/drivers/acpi/dock.c b/drivers/acpi/dock.c
>> > index b5e4142..0b3072c 100644
>> > --- a/drivers/acpi/dock.c
>> > +++ b/drivers/acpi/dock.c
>> > @@ -281,11 +281,15 @@ EXPORT_SYMBOL_GPL(is_dock_device);
>> >  */
>> >  struct device **dock_link_device(acpi_handle handle)
>> >  {
>> > -       struct device *dev = acpi_get_physical_device(handle);
>> > +       struct device *dev;
>> >        struct dock_station *dock_station;
>> >        int ret, dock = 0;
>> >        struct device **devices;
>> >
>> > +       if (!dock_station_count)
>> > +               return NULL;
>> > +
>> > +       dev = acpi_get_physical_device(handle);
>> >        devices = kmalloc(dock_station_count * sizeof(struct device *),
>> >                          GFP_KERNEL);
>> >
>> > @@ -320,12 +324,17 @@ EXPORT_SYMBOL_GPL(dock_link_device);
>> >  */
>> >  struct device **dock_unlink_device(acpi_handle handle)
>> >  {
>> > -       struct device *dev = acpi_get_physical_device(handle);
>> > +       struct device *dev;
>> >        struct dock_station *dock_station;
>> >        int dock = 0;
>> > -       struct device **devices =
>> > -               kmalloc(dock_station_count * sizeof(struct device *),
>> > -                       GFP_KERNEL);
>> > +       struct device **devices;
>> > +
>> > +       if (!dock_station_count)
>> > +               return NULL;
>> > +
>> > +       dev = acpi_get_physical_device(handle);
>> > +       devices = kmalloc(dock_station_count * sizeof(struct device *),
>> > +                         GFP_KERNEL);
>> >
>>
>> If bail out in this way, another patch looks needed to fix up
>> mem leakage :-(
>
> Sorry if I'm a little slow...but where is the leakage? The function
> doesn't allocate anything before bailing out in the dock_station_count
> check. And the rerun value should be freed by the caller. Please point
> me in the right direction.
>

Hi  Holger

Lets check the following snippet from what you posted,

> @@ -320,12 +324,17 @@ EXPORT_SYMBOL_GPL(dock_link_device);
>  */
>  struct device **dock_unlink_device(acpi_handle handle)
>  {
> -       struct device *dev = acpi_get_physical_device(handle);
> +       struct device *dev;
>        struct dock_station *dock_station;
>        int dock = 0;
> -       struct device **devices =
> -               kmalloc(dock_station_count * sizeof(struct device *),
> -                       GFP_KERNEL);
> +       struct device **devices;
> +
> +       if (!dock_station_count)
> +               return NULL;
> +
> +       dev = acpi_get_physical_device(handle);
> +       devices = kmalloc(dock_station_count * sizeof(struct device *),
> +                         GFP_KERNEL);
>
>        if (!dev)
>                return NULL;  <=== here return without freeing the newly
                                               allocated devices after checking
                                               dock_station_count is not zero
> --
> 1.7.7
>
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