USB: don't try to kzalloc 0 bytes

This patch (as907) prevents us from trying to allocate 0 bytes
when an interface has no endpoint descriptors.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/config.c

@@ -185,10 +185,12 @@ static int usb_parse_interface(struct device *ddev, int cfgno,
 		num_ep = USB_MAXENDPOINTS;
 	}
 
-	len = sizeof(struct usb_host_endpoint) * num_ep;
-	alt->endpoint = kzalloc(len, GFP_KERNEL);
-	if (!alt->endpoint)
-		return -ENOMEM;
+	if (num_ep > 0) {	/* Can't allocate 0 bytes */
+		len = sizeof(struct usb_host_endpoint) * num_ep;
+		alt->endpoint = kzalloc(len, GFP_KERNEL);
+		if (!alt->endpoint)
+			return -ENOMEM;
+	}
 
 	/* Parse all the endpoint descriptors */
 	n = 0;