USB: core: Change usb_get_device_descriptor() API

The usb_get_device_descriptor() routine reads the device descriptor
from the udev device and stores it directly in udev->descriptor.  This
interface is error prone, because the USB subsystem expects in-memory
copies of a device's descriptors to be immutable once the device has
been initialized.

The interface is changed so that the device descriptor is left in a
kmalloc-ed buffer, not copied into the usb_device structure.  A
pointer to the buffer is returned to the caller, who is then
responsible for kfree-ing it.  The corresponding changes needed in the
various callers are fairly small.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/d0111bb6-56c1-4f90-adf2-6cfe152f6561@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 23 insertions, 21 deletions

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 91abcd904d04..9279c8ccbcf2 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2694,12 +2694,17 @@ int usb_authorize_device(struct usb_device *usb_dev)
 	}
 
 	if (usb_dev->wusb) {
-		result = usb_get_device_descriptor(usb_dev, sizeof(usb_dev->descriptor));
-		if (result < 0) {
+		struct usb_device_descriptor *descr;
+
+		descr = usb_get_device_descriptor(usb_dev);
+		if (IS_ERR(descr)) {
+			result = PTR_ERR(descr);
 			dev_err(&usb_dev->dev, "can't re-read device descriptor for "
 				"authorization: %d\n", result);
 			goto error_device_descriptor;
 		}
+		usb_dev->descriptor = *descr;
+		kfree(descr);
 	}
 
 	usb_dev->authorized = 1;
@@ -4827,7 +4832,7 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
 	const char		*driver_name;
 	bool			do_new_scheme;
 	int			maxp0;
-	struct usb_device_descriptor	*buf;
+	struct usb_device_descriptor	*buf, *descr;
 
 	buf = kmalloc(GET_DESCRIPTOR_BUFSIZE, GFP_NOIO);
 	if (!buf)
@@ -5069,15 +5074,16 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
 		usb_ep0_reinit(udev);
 	}
 
-	retval = usb_get_device_descriptor(udev, USB_DT_DEVICE_SIZE);
-	if (retval < (signed)sizeof(udev->descriptor)) {
+	descr = usb_get_device_descriptor(udev);
+	if (IS_ERR(descr)) {
+		retval = PTR_ERR(descr);
 		if (retval != -ENODEV)
 			dev_err(&udev->dev, "device descriptor read/all, error %d\n",
 					retval);
-		if (retval >= 0)
-			retval = -ENOMSG;
 		goto fail;
 	}
+	udev->descriptor = *descr;
+	kfree(descr);
 
 	/*
 	 * Some superspeed devices have finished the link training process
@@ -5196,7 +5202,7 @@ hub_power_remaining(struct usb_hub *hub)
 
 
 static int descriptors_changed(struct usb_device *udev,
-		struct usb_device_descriptor *old_device_descriptor,
+		struct usb_device_descriptor *new_device_descriptor,
 		struct usb_host_bos *old_bos)
 {
 	int		changed = 0;
@@ -5207,8 +5213,8 @@ static int descriptors_changed(struct usb_device *udev,
 	int		length;
 	char		*buf;
 
-	if (memcmp(&udev->descriptor, old_device_descriptor,
-			sizeof(*old_device_descriptor)) != 0)
+	if (memcmp(&udev->descriptor, new_device_descriptor,
+			sizeof(*new_device_descriptor)) != 0)
 		return 1;
 
 	if ((old_bos && !udev->bos) || (!old_bos && udev->bos))
@@ -5533,9 +5539,8 @@ static void hub_port_connect_change(struct usb_hub *hub, int port1,
 {
 	struct usb_port *port_dev = hub->ports[port1 - 1];
 	struct usb_device *udev = port_dev->child;
-	struct usb_device_descriptor descriptor;
+	struct usb_device_descriptor *descr;
 	int status = -ENODEV;
-	int retval;
 
 	dev_dbg(&port_dev->dev, "status %04x, change %04x, %s\n", portstatus,
 			portchange, portspeed(hub, portstatus));
@@ -5562,23 +5567,20 @@ static void hub_port_connect_change(struct usb_hub *hub, int port1,
 			 * changed device descriptors before resuscitating the
 			 * device.
 			 */
-			descriptor = udev->descriptor;
-			retval = usb_get_device_descriptor(udev,
-					sizeof(udev->descriptor));
-			if (retval < 0) {
+			descr = usb_get_device_descriptor(udev);
+			if (IS_ERR(descr)) {
 				dev_dbg(&udev->dev,
-						"can't read device descriptor %d\n",
-						retval);
+						"can't read device descriptor %ld\n",
+						PTR_ERR(descr));
 			} else {
-				if (descriptors_changed(udev, &descriptor,
+				if (descriptors_changed(udev, descr,
 						udev->bos)) {
 					dev_dbg(&udev->dev,
 							"device descriptor has changed\n");
-					/* for disconnect() calls */
-					udev->descriptor = descriptor;
 				} else {
 					status = 0; /* Nothing to do */
 				}
+				kfree(descr);
 			}
 #ifdef CONFIG_PM
 		} else if (udev->state == USB_STATE_SUSPENDED &&