[PATCH 5.10 306/406] USB: core: Change usb_get_device_descriptor() API

Greg Kroah-Hartman
2023-09-17T19:38:05Z

From: Alan Stern <stern@rowland.harvard.edu>

commit de28e469da75359a2bb8cd8778b78aa64b1be1f4 upstream.

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>
---
drivers/usb/core/hcd.c | 10 +++++++---
drivers/usb/core/hub.c | 44 +++++++++++++++++++++++---------------------
drivers/usb/core/message.c | 29 ++++++++++++-----------------
drivers/usb/core/usb.h | 4 ++--
4 files changed, 44 insertions(+), 43 deletions(-)

--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -982,6 +982,7 @@ static int register_root_hub(struct usb_
{
struct device *parent_dev = hcd->self.controller;
struct usb_device *usb_dev = hcd->self.root_hub;
+ struct usb_device_descriptor *descr;
const int devnum = 1;
int retval;

@@ -993,13 +994,16 @@ static int register_root_hub(struct usb_
mutex_lock(&usb_bus_idr_lock);

usb_dev->ep0.desc.wMaxPacketSize = cpu_to_le16(64);
- retval = usb_get_device_descriptor(usb_dev, USB_DT_DEVICE_SIZE);
- if (retval != sizeof usb_dev->descriptor) {
+ descr = usb_get_device_descriptor(usb_dev);
+ if (IS_ERR(descr)) {
+ retval = PTR_ERR(descr);
mutex_unlock(&usb_bus_idr_lock);
dev_dbg (parent_dev, "can't read %s device descriptor %d\n",
dev_name(&usb_dev->dev), retval);
- return (retval < 0) ? retval : -EMSGSIZE;
+ return retval;
}
+ usb_dev->descriptor = *descr;
+ kfree(descr);

if (le16_to_cpu(usb_dev->descriptor.bcdUSB) >= 0x0201) {
retval = usb_get_bos_descriptor(usb_dev);
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2646,12 +2646,17 @@ int usb_authorize_device(struct usb_devi
}

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;
@@ -4680,7 +4685,7 @@ hub_port_init(struct usb_hub *hub, struc
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)
@@ -4913,15 +4918,16 @@ hub_port_init(struct usb_hub *hub, struc
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
@@ -5038,7 +5044,7 @@ 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;
@@ -5049,8 +5055,8 @@ static int descriptors_changed(struct us
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))
@@ -5370,9 +5376,8 @@ static void hub_port_connect_change(stru
{
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));
@@ -5399,23 +5404,20 @@ static void hub_port_connect_change(stru
* 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 &&
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1039,39 +1039,34 @@ char *usb_cache_string(struct usb_device
}

/*
- * usb_get_device_descriptor - (re)reads the device descriptor (usbcore)
- * @dev: the device whose device descriptor is being updated
- * @size: how much of the descriptor to read
+ * usb_get_device_descriptor - read the device descriptor
+ * @udev: the device whose device descriptor should be read
* Context: !in_interrupt ()
*
- * Updates the copy of the device descriptor stored in the device structure,
- * which dedicates space for this purpose.
- *
* Not exported, only for use by the core. If drivers really want to read
* the device descriptor directly, they can call usb_get_descriptor() with
* type = USB_DT_DEVICE and index = 0.
*
- * This call is synchronous, and may not be used in an interrupt context.
- *
- * Return: The number of bytes received on success, or else the status code
- * returned by the underlying usb_control_msg() call.
+ * Returns: a pointer to a dynamically allocated usb_device_descriptor
+ * structure (which the caller must deallocate), or an ERR_PTR value.
*/
-int usb_get_device_descriptor(struct usb_device *dev, unsigned int size)
+struct usb_device_descriptor *usb_get_device_descriptor(struct usb_device *udev)
{
struct usb_device_descriptor *desc;
int ret;

- if (size > sizeof(*desc))
- return -EINVAL;
desc = kmalloc(sizeof(*desc), GFP_NOIO);
if (!desc)
- return -ENOMEM;
+ return ERR_PTR(-ENOMEM);
+
+ ret = usb_get_descriptor(udev, USB_DT_DEVICE, 0, desc, sizeof(*desc));
+ if (ret == sizeof(*desc))
+ return desc;

- ret = usb_get_descriptor(dev, USB_DT_DEVICE, 0, desc, size);
if (ret >= 0)
- memcpy(&dev->descriptor, desc, size);
+ ret = -EMSGSIZE;
kfree(desc);
- return ret;
+ return ERR_PTR(ret);
}

/*
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -42,8 +42,8 @@ extern bool usb_endpoint_is_ignored(stru
struct usb_endpoint_descriptor *epd);
extern int usb_remove_device(struct usb_device *udev);

-extern int usb_get_device_descriptor(struct usb_device *dev,
- unsigned int size);
+extern struct usb_device_descriptor *usb_get_device_descriptor(
+ struct usb_device *udev);
extern int usb_set_isoch_delay(struct usb_device *dev);
extern int usb_get_bos_descriptor(struct usb_device *dev);
extern void usb_release_bos_descriptor(struct usb_device *dev);