staging: gigaset: fix illegal free on probe errors

BugLink: https://bugs.launchpad.net/bugs/1858489

commit 84f60ca7 upstream.

The driver failed to initialise its receive-buffer pointer, something
which could lead to an illegal free on late probe errors.

Fix this by making sure to clear all driver data at allocation.

Fixes: 2032e2c2 ("usb_gigaset: code cleanup")
Cc: stable <stable@vger.kernel.org>     # 2.6.33
Cc: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191202085610.12719-3-johan@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/isdn/gigaset/usb-gigaset.c

@@ -574,8 +574,7 @@ static int gigaset_initcshw(struct cardstate *cs)
 {
 	struct usb_cardstate *ucs;
 
-	cs->hw.usb = ucs =
-		kmalloc(sizeof(struct usb_cardstate), GFP_KERNEL);
+	cs->hw.usb = ucs = kzalloc(sizeof(struct usb_cardstate), GFP_KERNEL);
 	if (!ucs) {
 		pr_err("out of memory\n");
 		return -ENOMEM;
@@ -587,9 +586,6 @@ static int gigaset_initcshw(struct cardstate *cs)
 	ucs->bchars[3] = 0;
 	ucs->bchars[4] = 0x11;
 	ucs->bchars[5] = 0x13;
-	ucs->bulk_out_buffer = NULL;
-	ucs->bulk_out_urb = NULL;
-	ucs->read_urb = NULL;
 	tasklet_init(&cs->write_tasklet,
 		     gigaset_modem_fill, (unsigned long) cs);