Commit f0688c8b authored Jun 17, 2014 by Michal Nazarewicz Committed by Felipe Balbi Jun 19, 2014

usb: gadget: f_fs: fix NULL pointer dereference when there are no strings



If the descriptors do not need any strings and user space sends empty
set of strings, the ffs->stringtabs field remains NULL.  Thus
*ffs->stringtabs in functionfs_bind leads to a NULL pointer
dereferenece.

The bug was introduced by commit [fd7c9a00: “use usb_string_ids_n()”].

While at it, remove double initialisation of lang local variable in
that function.

ffs->strings_count does not need to be checked in any way since in
the above scenario it will remain zero and usb_string_ids_n() is
a no-operation when colled with 0 argument.

Cc: <stable@vger.kernel.org>  # v2.6.36+
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

parent 82363cf2

drivers/usb/gadget/f_fs.c

+7 −5

Original line number	Original line	Diff line number	Diff line
	@@ -1483,12 +1483,14 @@ static int functionfs_bind(struct ffs_data ffs, struct usb_composite_dev cdev)
	ffs->ep0req->context = ffs;		ffs->ep0req->context = ffs;

	lang = ffs->stringtabs;		lang = ffs->stringtabs;
	for (lang = ffs->stringtabs; *lang; ++lang) {		if (lang) {
			for (; *lang; ++lang) {
	struct usb_string str = (lang)->strings;		struct usb_string str = (lang)->strings;
	int id = first_id;		int id = first_id;
	for (; str->s; ++id, ++str)		for (; str->s; ++id, ++str)
	str->id = id;		str->id = id;
	}		}
			}

	ffs->gadget = cdev->gadget;		ffs->gadget = cdev->gadget;
	ffs_data_get(ffs);		ffs_data_get(ffs);