linux-kernel - [PATCH 3.16 193/254] USB: UDC core: fix double-free in usb_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,
        "Felipe Balbi" <felipe.balbi@...ux.intel.com>,
        "Peter Chen" <peter.chen@....com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Fengguang Wu" <fengguang.wu@...el.com>,
        "Alan Stern" <stern@...land.harvard.edu>
Subject: [PATCH 3.16 193/254] USB: UDC core: fix double-free in
 usb_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 7ae2c3c280db183ca9ada2675c34ec2f7378abfa upstream.

The error-handling pathways in usb_add_gadget_udc_release() are messed
up.  Aside from the uninformative statement labels, they can deallocate
the udc structure after calling put_device(), which is a double-free.
This was observed by KASAN in automatic testing.

This patch cleans up the routine.  It preserves the requirement that
when any failure occurs, we call put_device(&gadget->dev).

Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Reported-by: Fengguang Wu <fengguang.wu@...el.com>
Reviewed-by: Peter Chen <peter.chen@....com>
Acked-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.16:
 - The err5 path is not presnet
 - Adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/drivers/usb/gadget/udc-core.c
+++ b/drivers/usb/gadget/udc-core.c
@@ -219,11 +219,7 @@ int usb_add_gadget_udc_release(struct de
 
 	udc = kzalloc(sizeof(*udc), GFP_KERNEL);
 	if (!udc)
-		goto err1;
-
-	ret = device_add(&gadget->dev);
-	if (ret)
-		goto err2;
+		goto err_put_gadget;
 
 	device_initialize(&udc->dev);
 	udc->dev.release = usb_udc_release;
@@ -232,7 +228,11 @@ int usb_add_gadget_udc_release(struct de
 	udc->dev.parent = parent;
 	ret = dev_set_name(&udc->dev, "%s", kobject_name(&parent->kobj));
 	if (ret)
-		goto err3;
+		goto err_put_udc;
+
+	ret = device_add(&gadget->dev);
+	if (ret)
+		goto err_put_udc;
 
 	udc->gadget = gadget;
 
@@ -241,7 +241,7 @@ int usb_add_gadget_udc_release(struct de
 
 	ret = device_add(&udc->dev);
 	if (ret)
-		goto err4;
+		goto err_unlist_udc;
 
 	usb_gadget_set_state(gadget, USB_STATE_NOTATTACHED);
 
@@ -249,18 +249,16 @@ int usb_add_gadget_udc_release(struct de
 
 	return 0;
 
-err4:
+ err_unlist_udc:
 	list_del(&udc->list);
 	mutex_unlock(&udc_lock);
 
-err3:
-	put_device(&udc->dev);
 	device_del(&gadget->dev);
 
-err2:
-	kfree(udc);
+ err_put_udc:
+	put_device(&udc->dev);
 
-err1:
+ err_put_gadget:
 	put_device(&gadget->dev);
 	return ret;
 }