USB: Gadget core: fix inconsistency in the interface tousb_add_gadget_udc_release()

commit afd7fd81f22bf90474216515dbd6088f9bd70343 upstream.

The usb_add_gadget_udc_release() routine in the USB gadget core will
sometimes but not always call the gadget's release function when an
error occurs.  More specifically, if the struct usb_udc allocation
fails then the release function is not called, and for other errors it
is.

As a result, users of this routine cannot know whether they need to
deallocate the memory containing the gadget structure following an
error.  This leads to unavoidable memory leaks or double frees.

This patch fixes the problem by splitting the existing
device_register() call into device_initialize() and device_add(), and
doing the udc allocation in between.  That way, even if the allocation
fails it is still possible to call device_del(), and so the release
function will be always called following an error.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/gadget/udc-core.c b/drivers/usb/gadget/udc-core.c
index a93d7439b9e5a320f4af8b03f7873f16829b4ca3..5299ecd75003582141f55edd9734d7f829aa5bb1 100644 (file)
--- a/drivers/usb/gadget/udc-core.c
+++ b/drivers/usb/gadget/udc-core.c
@@ -192,6 +192,7 @@ static void usb_udc_nop_release(struct device *dev)
  * @release: a gadget release function.
  *
  * Returns zero on success, negative errno otherwise.
+ * Calls the gadget release function in the latter case.
  */
 int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
                void (*release)(struct device *dev))
@@ -199,10 +200,6 @@ int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
        struct usb_udc          *udc;
        int                     ret = -ENOMEM;
 
-       udc = kzalloc(sizeof(*udc), GFP_KERNEL);
-       if (!udc)
-               goto err1;
-
        dev_set_name(&gadget->dev, "gadget");
        INIT_WORK(&gadget->work, usb_gadget_state_work);
        gadget->dev.parent = parent;
@@ -218,7 +215,13 @@ int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
        else
                gadget->dev.release = usb_udc_nop_release;
 
-       ret = device_register(&gadget->dev);
+       device_initialize(&gadget->dev);
+
+       udc = kzalloc(sizeof(*udc), GFP_KERNEL);
+       if (!udc)
+               goto err1;
+
+       ret = device_add(&gadget->dev);
        if (ret)
                goto err2;
 
@@ -255,10 +258,10 @@ err3:
        device_del(&gadget->dev);
 
 err2:
-       put_device(&gadget->dev);
        kfree(udc);
 
 err1:
+       put_device(&gadget->dev);
        return ret;
 }
 EXPORT_SYMBOL_GPL(usb_add_gadget_udc_release);