linux-kernel - [PATCH 3.16 192/254] USB: Gadget core: fix inconsistency in the interface tousb_add_gadget_udc

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Date:   Wed, 28 Feb 2018 15:20:18 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Alan Stern" <stern@...land.harvard.edu>,
        "Alexey Khoroshilov" <khoroshilov@...ras.ru>,
        "Felipe Balbi" <felipe.balbi@...ux.intel.com>
Subject: [PATCH 3.16 192/254] USB: Gadget core: fix inconsistency in the
 interface tousb_add_gadget_udc_release()

3.16.55-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Alan Stern <stern@...land.harvard.edu>

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@...land.harvard.edu>
Reported-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
Signed-off-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/gadget/udc-core.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- 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 d
  * @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 de
 	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 de
 	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);