Patch "usb: gadget: composite: Fix use-after-free in usb_composite_overwrite_options" has been added to the 3.18-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    usb: gadget: composite: Fix use-after-free in usb_composite_overwrite_options

to the 3.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     usb-gadget-composite-fix-use-after-free-in-usb_composite_overwrite_options.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From aec17e1e249567e82b26dafbb86de7d07fde8729 Mon Sep 17 00:00:00 2001
From: Andrew Gabbasov <andrew_gabbasov@mentor.com>
Date: Sat, 30 Sep 2017 08:55:55 -0700
Subject: usb: gadget: composite: Fix use-after-free in usb_composite_overwrite_options

From: Andrew Gabbasov <andrew_gabbasov@mentor.com>

commit aec17e1e249567e82b26dafbb86de7d07fde8729 upstream.

KASAN enabled configuration reports an error

    BUG: KASAN: use-after-free in usb_composite_overwrite_options+...
                [libcomposite] at addr ...
    Read of size 1 by task ...

when some driver is un-bound and then bound again.
For example, this happens with FunctionFS driver when "ffs-test"
test application is run several times in a row.

If the driver has empty manufacturer ID string in initial static data,
it is then replaced with generated string. After driver unbinding
the generated string is freed, but the driver data still keep that
pointer. And if the driver is then bound again, that pointer
is re-used for string emptiness check.

The fix is to clean up the driver string data upon its unbinding
to drop the pointer to freed memory.

Fixes: cc2683c318a5 ("usb: gadget: Provide a default implementation of default manufacturer string")
Signed-off-by: Andrew Gabbasov <andrew_gabbasov@mentor.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/gadget/composite.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -1806,6 +1806,8 @@ static DEVICE_ATTR_RO(suspended);
 static void __composite_unbind(struct usb_gadget *gadget, bool unbind_driver)
 {
 	struct usb_composite_dev	*cdev = get_gadget_data(gadget);
+	struct usb_gadget_strings	*gstr = cdev->driver->strings[0];
+	struct usb_string		*dev_str = gstr->strings;
 
 	/* composite_disconnect() must already have been called
 	 * by the underlying peripheral controller driver!
@@ -1825,6 +1827,9 @@ static void __composite_unbind(struct us
 
 	composite_dev_cleanup(cdev);
 
+	if (dev_str[USB_GADGET_MANUFACTURER_IDX].s == cdev->def_manufacturer)
+		dev_str[USB_GADGET_MANUFACTURER_IDX].s = "";
+
 	kfree(cdev->def_manufacturer);
 	kfree(cdev);
 	set_gadget_data(gadget, NULL);


Patches currently in stable-queue which might be from andrew_gabbasov@mentor.com are

queue-3.18/usb-gadget-composite-fix-use-after-free-in-usb_composite_overwrite_options.patch