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SubjectRe: [PATCH] USB: Gadget: Composite: Added error handling codes to prevent a memory leak case when the configuration's bind function failed
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On Thu, 15 Mar 2012 02:23:55 +0100, <Yongsul@vger.kernel.org> wrote:
> In some usb gadget driver, for example usb gadget serial driver(serial.c),
> multifunction composite driver(multi,c), nokia composite gadget driver(nokia.c),
> HID composite driver(hid.c), CDC composite driver(cdc2.c).., the configuration's
> bind function by called the 'usb_add_config()' has multiple bind config functions
> for each functionality, for example cdc2 configuration bind function -'cdc_do_config()'
> has two functionality bind config functions -'ecm_bind_config()' & 'acm_bind_config()'
> in CDC composite driver.
> In each functionality bind config function, new instance for each functionality is
> allocated & initialized by 'kzalloc()' ,and finally the new instance is added by
> 'usb_add_function()'. After 'usb_add_function' state, already created the instance
> is only handled by its configuration & freed from functionality unbind function.
> So, If an error occurred during the second functionality bind config state, for example
> an error occurred at 'acm_bind_config()' after succeeding 'ecm_bind_function()',
> The created instance by 'acm_bind_config()' cannot be freed.
> And it makes memory leak situation.

It may be my poor English skills, but this is very hard to read.

Also, should this be handled in usb_gadget_probe_driver() instead? Ie. on error
recovery path, should usb_gadget_probe_driver() call usb_gadget_remove_driver()?

In particular, if I'm not mistaken, for (some?) gadgets with two configurations
(like g_multi), if the second configuration fails, the first one will not get
removed, so the memory will still leak, no?

> Signed-off-by: yongsul96.oh@samsung.com <yongsul96.oh@samsung.com>
> ---
> drivers/usb/gadget/composite.c | 13 +++++++++++++
> 1 files changed, 13 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> index baaebf2..4cb1801 100644
> --- a/drivers/usb/gadget/composite.c
> +++ b/drivers/usb/gadget/composite.c
> @@ -737,6 +737,19 @@ int usb_add_config(struct usb_composite_dev *cdev,
> status = bind(config);
> if (status < 0) {
> + while (!list_empty(&config->functions)) {
> + struct usb_function *f;
> +
> + f = list_first_entry(&config->functions,
> + struct usb_function, list);
> + list_del(&f->list);
> + if (f->unbind) {
> + DBG(cdev, "unbind function '%s'/%p\n",
> + f->name, f);
> + f->unbind(config, f);
> + /* may free memory for "f" */
> + }
> + }
> list_del(&config->list);
> config->cdev = NULL;
> } else {


--
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.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
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