[PATCH 3.16 193/254] USB: UDC core: fix double-free in usb_add_gadget_udc_release

[Ben Hutchings]

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

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

From: Alan Stern <st...@rowland.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 <st...@rowland.harvard.edu>
Reported-by: Fengguang Wu <fengguang...@intel.com>
Reviewed-by: Peter Chen <peter.c...@nxp.com>
Acked-by: Felipe Balbi <felipe.ba...@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
[bwh: Backported to 3.16:
 - The err5 path is not presnet
 - Adjust filename]
Signed-off-by: Ben Hutchings <b...@decadent.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;
 }