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Message-ID: <CACGdZYL_dPFp-yHWHGC3vxyv4R4dYtSJe5GPcN0NjG2qaz+xmg@mail.gmail.com>
Date: Tue, 25 Jul 2023 13:42:01 -0700
From: Khazhy Kumykov <khazhy@...gle.com>
To: Alan Stern <stern@...land.harvard.edu>
Cc: syzbot <syzbot+18996170f8096c6174d0@...kaller.appspotmail.com>,
gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
linux-usb@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [usb?] KASAN: slab-out-of-bounds Read in
read_descriptors (3)
On Tue, Jul 25, 2023 at 12:26 PM Alan Stern <stern@...land.harvard.edu> wrote:
>
> On Sat, Jul 22, 2023 at 07:21:23PM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot has tested the proposed patch and the reproducer did not trigger any issue:
> >
> > Reported-and-tested-by: syzbot+18996170f8096c6174d0@...kaller.appspotmail.com
>
> Here's a revised version of the patch, with some mistakes fixed. If
> this works, I'll split it into three parts and submit them.
>
> Alan Stern
>
> #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ v6.5-rc3
>
> Index: usb-devel/drivers/usb/core/hub.c
> ===================================================================
> --- usb-devel.orig/drivers/usb/core/hub.c
> +++ usb-devel/drivers/usb/core/hub.c
> @@ -2671,12 +2671,17 @@ 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;
Hmm, in your first patch you rejected diffs to the descriptor here,
which might be necessary - since we don't re-initialize the device so
can get a similar issue if the bad usb device decides to change
bNumConfigurations to cause a buffer overrun. (This also stuck out to
me as an exception to the "descriptors should be immutable" comment
later in the patch.
> + kfree(descr);
> }
>
> usb_dev->authorized = 1;
> @@ -4718,6 +4723,67 @@ static int hub_enable_device(struct usb_
> return hcd->driver->enable_device(hcd, udev);
> }
>
> +/*
> + * Get the bMaxPacketSize0 value during initialization by reading the
> + * device's device descriptor. Since we don't already know this value,
> + * the transfer is unsafe and it ignores I/O errors, only testing for
> + * reasonable received values.
> + *
> + * For "old scheme" initialization size will be 8, so we read just the
> + * start of the device descriptor, which should work okay regardless of
> + * the actual bMaxPacketSize0 value. For "new scheme" initialization,
> + * size will be 64 (and buf will point to a sufficiently large buffer),
> + * which might not be kosher according to the USB spec but it's what
> + * Windows does and what many devices expect.
> + *
> + * Returns bMaxPacketSize0 or a negative error code.
> + */
> +static int get_bMaxPacketSize0(struct usb_device *udev,
> + struct usb_device_descriptor *buf, int size, bool first_time)
> +{
> + int i, rc;
> +
> + /*
> + * Retry on all errors; some devices are flakey.
> + * 255 is for WUSB devices, we actually need to use
> + * 512 (WUSB1.0[4.8.1]).
> + */
> + for (i = 0; i < GET_MAXPACKET0_TRIES; ++i) {
> + /* Start with invalid values in case the transfer fails */
> + buf->bDescriptorType = buf->bMaxPacketSize0 = 0;
> + rc = usb_control_msg(udev, usb_rcvaddr0pipe(),
> + USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
> + USB_DT_DEVICE << 8, 0,
> + buf, size,
> + initial_descriptor_timeout);
> + switch (buf->bMaxPacketSize0) {
> + case 8: case 16: case 32: case 64: case 255:
> + if (buf->bDescriptorType == USB_DT_DEVICE) {
> + rc = buf->bMaxPacketSize0;
> + break;
> + }
> + fallthrough;
> + default:
> + if (rc >= 0)
> + rc = -EPROTO;
> + break;
> + }
> +
> + /*
> + * Some devices time out if they are powered on
> + * when already connected. They need a second
> + * reset, so return early. But only on the first
> + * attempt, lest we get into a time-out/reset loop.
> + */
> + if (rc > 0 || (rc == -ETIMEDOUT && first_time &&
> + udev->speed > USB_SPEED_FULL))
> + break;
> + }
> + return rc;
> +}
> +
> +#define GET_DESCRIPTOR_BUFSIZE 64
> +
> /* Reset device, (re)assign address, get device descriptor.
> * Device connection must be stable, no more debouncing needed.
> * Returns device in USB_STATE_ADDRESS, except on error.
> @@ -4727,10 +4793,17 @@ static int hub_enable_device(struct usb_
> * the port lock. For a newly detected device that is not accessible
> * through any global pointers, it's not necessary to lock the device,
> * but it is still necessary to lock the port.
> + *
> + * For a newly detected device, @dev_descr must be NULL. The device
> + * descriptor retrieved from the device will then be stored in
> + * @udev->descriptor. For an already existing device, @dev_descr
> + * must be non-NULL. The device descriptor will be stored there,
> + * not in @udev->descriptor, because descriptors for registered
> + * devices are meant to be immutable.
> */
> static int
> hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
> - int retry_counter)
> + int retry_counter, struct usb_device_descriptor *dev_descr)
> {
> struct usb_device *hdev = hub->hdev;
> struct usb_hcd *hcd = bus_to_hcd(hdev->bus);
> @@ -4742,6 +4815,13 @@ hub_port_init(struct usb_hub *hub, struc
> int devnum = udev->devnum;
> const char *driver_name;
> bool do_new_scheme;
> + const bool initial = !dev_descr;
> + int maxp0;
> + struct usb_device_descriptor *buf, *descr;
> +
> + buf = kmalloc(GET_DESCRIPTOR_BUFSIZE, GFP_NOIO);
> + if (!buf)
> + return -ENOMEM;
>
> /* root hub ports have a slightly longer reset period
> * (from USB 2.0 spec, section 7.1.7.5)
> @@ -4774,32 +4854,34 @@ hub_port_init(struct usb_hub *hub, struc
> }
> oldspeed = udev->speed;
>
> - /* USB 2.0 section 5.5.3 talks about ep0 maxpacket ...
> - * it's fixed size except for full speed devices.
> - * For Wireless USB devices, ep0 max packet is always 512 (tho
> - * reported as 0xff in the device descriptor). WUSB1.0[4.8.1].
> - */
> - switch (udev->speed) {
> - case USB_SPEED_SUPER_PLUS:
> - case USB_SPEED_SUPER:
> - case USB_SPEED_WIRELESS: /* fixed at 512 */
> - udev->ep0.desc.wMaxPacketSize = cpu_to_le16(512);
> - break;
> - case USB_SPEED_HIGH: /* fixed at 64 */
> - udev->ep0.desc.wMaxPacketSize = cpu_to_le16(64);
> - break;
> - case USB_SPEED_FULL: /* 8, 16, 32, or 64 */
> - /* to determine the ep0 maxpacket size, try to read
> - * the device descriptor to get bMaxPacketSize0 and
> - * then correct our initial guess.
> - */
> - udev->ep0.desc.wMaxPacketSize = cpu_to_le16(64);
> - break;
> - case USB_SPEED_LOW: /* fixed at 8 */
> - udev->ep0.desc.wMaxPacketSize = cpu_to_le16(8);
> - break;
> - default:
> - goto fail;
> + if (initial) {
> + /* USB 2.0 section 5.5.3 talks about ep0 maxpacket ...
> + * it's fixed size except for full speed devices.
> + * For Wireless USB devices, ep0 max packet is always 512 (tho
> + * reported as 0xff in the device descriptor). WUSB1.0[4.8.1].
> + */
> + switch (udev->speed) {
> + case USB_SPEED_SUPER_PLUS:
> + case USB_SPEED_SUPER:
> + case USB_SPEED_WIRELESS: /* fixed at 512 */
> + udev->ep0.desc.wMaxPacketSize = cpu_to_le16(512);
> + break;
> + case USB_SPEED_HIGH: /* fixed at 64 */
> + udev->ep0.desc.wMaxPacketSize = cpu_to_le16(64);
> + break;
> + case USB_SPEED_FULL: /* 8, 16, 32, or 64 */
> + /* to determine the ep0 maxpacket size, try to read
> + * the device descriptor to get bMaxPacketSize0 and
> + * then correct our initial guess.
> + */
> + udev->ep0.desc.wMaxPacketSize = cpu_to_le16(64);
> + break;
> + case USB_SPEED_LOW: /* fixed at 8 */
> + udev->ep0.desc.wMaxPacketSize = cpu_to_le16(8);
> + break;
> + default:
> + goto fail;
> + }
> }
>
> if (udev->speed == USB_SPEED_WIRELESS)
> @@ -4822,22 +4904,24 @@ hub_port_init(struct usb_hub *hub, struc
> if (udev->speed < USB_SPEED_SUPER)
> dev_info(&udev->dev,
> "%s %s USB device number %d using %s\n",
> - (udev->config) ? "reset" : "new", speed,
> + (initial ? "new" : "reset"), speed,
> devnum, driver_name);
>
> - /* Set up TT records, if needed */
> - if (hdev->tt) {
> - udev->tt = hdev->tt;
> - udev->ttport = hdev->ttport;
> - } else if (udev->speed != USB_SPEED_HIGH
> - && hdev->speed == USB_SPEED_HIGH) {
> - if (!hub->tt.hub) {
> - dev_err(&udev->dev, "parent hub has no TT\n");
> - retval = -EINVAL;
> - goto fail;
> + if (initial) {
> + /* Set up TT records, if needed */
> + if (hdev->tt) {
> + udev->tt = hdev->tt;
> + udev->ttport = hdev->ttport;
> + } else if (udev->speed != USB_SPEED_HIGH
> + && hdev->speed == USB_SPEED_HIGH) {
> + if (!hub->tt.hub) {
> + dev_err(&udev->dev, "parent hub has no TT\n");
> + retval = -EINVAL;
> + goto fail;
> + }
> + udev->tt = &hub->tt;
> + udev->ttport = port1;
> }
> - udev->tt = &hub->tt;
> - udev->ttport = port1;
> }
>
> /* Why interleave GET_DESCRIPTOR and SET_ADDRESS this way?
> @@ -4861,9 +4945,6 @@ hub_port_init(struct usb_hub *hub, struc
> }
>
> if (do_new_scheme) {
> - struct usb_device_descriptor *buf;
> - int r = 0;
> -
> retval = hub_enable_device(udev);
> if (retval < 0) {
> dev_err(&udev->dev,
> @@ -4872,52 +4953,14 @@ hub_port_init(struct usb_hub *hub, struc
> goto fail;
> }
>
> -#define GET_DESCRIPTOR_BUFSIZE 64
> - buf = kmalloc(GET_DESCRIPTOR_BUFSIZE, GFP_NOIO);
> - if (!buf) {
> - retval = -ENOMEM;
> - continue;
> - }
> -
> - /* Retry on all errors; some devices are flakey.
> - * 255 is for WUSB devices, we actually need to use
> - * 512 (WUSB1.0[4.8.1]).
> - */
> - for (operations = 0; operations < GET_MAXPACKET0_TRIES;
> - ++operations) {
> - buf->bMaxPacketSize0 = 0;
> - r = usb_control_msg(udev, usb_rcvaddr0pipe(),
> - USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
> - USB_DT_DEVICE << 8, 0,
> - buf, GET_DESCRIPTOR_BUFSIZE,
> - initial_descriptor_timeout);
> - switch (buf->bMaxPacketSize0) {
> - case 8: case 16: case 32: case 64: case 255:
> - if (buf->bDescriptorType ==
> - USB_DT_DEVICE) {
> - r = 0;
> - break;
> - }
> - fallthrough;
> - default:
> - if (r == 0)
> - r = -EPROTO;
> - break;
> - }
> - /*
> - * Some devices time out if they are powered on
> - * when already connected. They need a second
> - * reset. But only on the first attempt,
> - * lest we get into a time out/reset loop
> - */
> - if (r == 0 || (r == -ETIMEDOUT &&
> - retries == 0 &&
> - udev->speed > USB_SPEED_FULL))
> - break;
> + maxp0 = get_bMaxPacketSize0(udev, buf,
> + GET_DESCRIPTOR_BUFSIZE, retries == 0);
> + if (maxp0 > 0 && !initial &&
> + maxp0 != udev->descriptor.bMaxPacketSize0) {
> + dev_err(&udev->dev, "device reset changed ep0 maxpacket size!\n");
> + retval = -ENODEV;
> + goto fail;
> }
> - udev->descriptor.bMaxPacketSize0 =
> - buf->bMaxPacketSize0;
> - kfree(buf);
>
> retval = hub_port_reset(hub, port1, udev, delay, false);
> if (retval < 0) /* error or disconnect */
> @@ -4928,14 +4971,13 @@ hub_port_init(struct usb_hub *hub, struc
> retval = -ENODEV;
> goto fail;
> }
> - if (r) {
> - if (r != -ENODEV)
> + if (maxp0 < 0) {
> + if (maxp0 != -ENODEV)
> dev_err(&udev->dev, "device descriptor read/64, error %d\n",
> - r);
> - retval = -EMSGSIZE;
> + maxp0);
> + retval = maxp0;
> continue;
> }
> -#undef GET_DESCRIPTOR_BUFSIZE
> }
>
> /*
> @@ -4981,18 +5023,22 @@ hub_port_init(struct usb_hub *hub, struc
> break;
> }
>
> - retval = usb_get_device_descriptor(udev, 8);
> - if (retval < 8) {
> + /* !do_new_scheme || wusb */
> + maxp0 = get_bMaxPacketSize0(udev, buf, 8, retries == 0);
> + if (maxp0 < 0) {
> + retval = maxp0;
> if (retval != -ENODEV)
> dev_err(&udev->dev,
> "device descriptor read/8, error %d\n",
> retval);
> - if (retval >= 0)
> - retval = -EMSGSIZE;
> } else {
> u32 delay;
>
> - retval = 0;
> + if (!initial && maxp0 != udev->descriptor.bMaxPacketSize0) {
> + dev_err(&udev->dev, "device reset changed ep0 maxpacket size!\n");
> + retval = -ENODEV;
> + goto fail;
> + }
>
> delay = udev->parent->hub_delay;
> udev->hub_delay = min_t(u32, delay,
> @@ -5010,27 +5056,10 @@ hub_port_init(struct usb_hub *hub, struc
> if (retval)
> goto fail;
>
> - /*
> - * Some superspeed devices have finished the link training process
> - * and attached to a superspeed hub port, but the device descriptor
> - * got from those devices show they aren't superspeed devices. Warm
> - * reset the port attached by the devices can fix them.
> - */
> - if ((udev->speed >= USB_SPEED_SUPER) &&
> - (le16_to_cpu(udev->descriptor.bcdUSB) < 0x0300)) {
> - dev_err(&udev->dev, "got a wrong device descriptor, "
> - "warm reset device\n");
> - hub_port_reset(hub, port1, udev,
> - HUB_BH_RESET_TIME, true);
> - retval = -EINVAL;
> - goto fail;
> - }
> -
> - if (udev->descriptor.bMaxPacketSize0 == 0xff ||
> - udev->speed >= USB_SPEED_SUPER)
> + if (maxp0 == 0xff || udev->speed >= USB_SPEED_SUPER)
> i = 512;
> else
> - i = udev->descriptor.bMaxPacketSize0;
> + i = maxp0;
> if (usb_endpoint_maxp(&udev->ep0.desc) != i) {
> if (udev->speed == USB_SPEED_LOW ||
> !(i == 8 || i == 16 || i == 32 || i == 64)) {
> @@ -5046,13 +5075,33 @@ 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;
> + }
> + if (initial)
> + udev->descriptor = *descr;
> + else
> + *dev_descr = *descr;
> + kfree(descr);
> +
> + /*
> + * Some superspeed devices have finished the link training process
> + * and attached to a superspeed hub port, but the device descriptor
> + * got from those devices show they aren't superspeed devices. Warm
> + * reset the port attached by the devices can fix them.
> + */
> + if ((udev->speed >= USB_SPEED_SUPER) &&
> + (le16_to_cpu(udev->descriptor.bcdUSB) < 0x0300)) {
> + dev_err(&udev->dev, "got a wrong device descriptor, "
> + "warm reset device\n");
> + hub_port_reset(hub, port1, udev,
> + HUB_BH_RESET_TIME, true);
> + retval = -EINVAL;
> goto fail;
> }
>
> @@ -5078,6 +5127,7 @@ fail:
> hub_port_disable(hub, port1, 0);
> update_devnum(udev, devnum); /* for disconnect processing */
> }
> + kfree(buf);
> return retval;
> }
>
> @@ -5158,7 +5208,7 @@ 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;
> @@ -5169,8 +5219,8 @@ 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))
> @@ -5348,7 +5398,7 @@ static void hub_port_connect(struct usb_
> }
>
> /* reset (non-USB 3.0 devices) and get descriptor */
> - status = hub_port_init(hub, udev, port1, i);
> + status = hub_port_init(hub, udev, port1, i, NULL);
> if (status < 0)
> goto loop;
>
> @@ -5495,9 +5545,8 @@ 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));
> @@ -5524,23 +5573,20 @@ 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 &&
> @@ -5982,7 +6028,7 @@ static int usb_reset_and_verify_device(s
> struct usb_device *parent_hdev = udev->parent;
> struct usb_hub *parent_hub;
> struct usb_hcd *hcd = bus_to_hcd(udev->bus);
> - struct usb_device_descriptor descriptor = udev->descriptor;
> + struct usb_device_descriptor descriptor;
> struct usb_host_bos *bos;
> int i, j, ret = 0;
> int port1 = udev->portnum;
> @@ -6018,7 +6064,7 @@ static int usb_reset_and_verify_device(s
> /* ep0 maxpacket size may change; let the HCD know about it.
> * Other endpoints will be handled by re-enumeration. */
> usb_ep0_reinit(udev);
> - ret = hub_port_init(parent_hub, udev, port1, i);
> + ret = hub_port_init(parent_hub, udev, port1, i, &descriptor);
Looks like this is the only caller that passes &descriptor, and it
just checks that it didn't change. Would it make sense to put the
enitre descriptors_changed stanza in hub_port_init, for the re-init
case?
> if (ret >= 0 || ret == -ENOTCONN || ret == -ENODEV)
> break;
> }
> @@ -6030,7 +6076,6 @@ static int usb_reset_and_verify_device(s
> /* Device might have changed firmware (DFU or similar) */
> if (descriptors_changed(udev, &descriptor, bos)) {
> dev_info(&udev->dev, "device firmware changed\n");
> - udev->descriptor = descriptor; /* for disconnect() calls */
> goto re_enumerate;
> }
>
> Index: usb-devel/drivers/usb/core/hcd.c
> ===================================================================
> --- usb-devel.orig/drivers/usb/core/hcd.c
> +++ usb-devel/drivers/usb/core/hcd.c
> @@ -983,6 +983,7 @@ 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;
>
> @@ -994,13 +995,16 @@ 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);
> Index: usb-devel/drivers/usb/core/message.c
> ===================================================================
> --- usb-devel.orig/drivers/usb/core/message.c
> +++ usb-devel/drivers/usb/core/message.c
> @@ -1040,40 +1040,35 @@ char *usb_cache_string(struct usb_device
> EXPORT_SYMBOL_GPL(usb_cache_string);
>
> /*
> - * 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: task context, might sleep.
> *
> - * 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);
> }
>
> /*
> Index: usb-devel/drivers/usb/core/usb.h
> ===================================================================
> --- usb-devel.orig/drivers/usb/core/usb.h
> +++ usb-devel/drivers/usb/core/usb.h
> @@ -43,8 +43,8 @@ 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);
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