Commit message: usbip: fix stub_send_ret_submit() vulnerability to null transfer_buffer

stub_send_ret_submit() handles urb with a potential null transfer_buffer,
when it replays a packet with potential malicious data that could contain
a null buffer. Add a check for the condition when actual_length > 0 and
transfer_buffer is null.

Reported-by: Secunia Research <vuln@secunia.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CVE: CVE-2017-16914
CWE: CWE-476
Vulnerability description: The "stub_send_ret_submit()" function (drivers/usb/usbip/stub_tx.c) in the Linux Kernel before version 4.14.8, 4.9.71, 4.1.49, and 4.4.107 allows attackers to cause a denial of service (NULL pointer dereference) via a specially crafted USB over IP packet.

Project: linux
File: stub_tx.c

static void setup_ret_unlink_pdu(struct usbip_header *rpdu,
				 struct stub_unlink *unlink)
{
	setup_base_pdu(&rpdu->base, USBIP_RET_UNLINK, unlink->seqnum);
	rpdu->u.ret_unlink.status = unlink->status;
}

Project: linux
File: stub_tx.c

static int stub_send_ret_unlink(struct stub_device *sdev)
{
	unsigned long flags;
	struct stub_unlink *unlink, *tmp;

	struct msghdr msg;
	struct kvec iov[1];
	size_t txsize;

	size_t total_size = 0;

	while ((unlink = dequeue_from_unlink_tx(sdev)) != NULL) {
		int ret;
		struct usbip_header pdu_header;

		txsize = 0;
		memset(&pdu_header, 0, sizeof(pdu_header));
		memset(&msg, 0, sizeof(msg));
		memset(&iov, 0, sizeof(iov));

		usbip_dbg_stub_tx("setup ret unlink %lu\n", unlink->seqnum);

		/* 1. setup usbip_header */
		setup_ret_unlink_pdu(&pdu_header, unlink);
		usbip_header_correct_endian(&pdu_header, 1);

		iov[0].iov_base = &pdu_header;
		iov[0].iov_len  = sizeof(pdu_header);
		txsize += sizeof(pdu_header);

		ret = kernel_sendmsg(sdev->ud.tcp_socket, &msg, iov,
				     1, txsize);
		if (ret != txsize) {
			dev_err(&sdev->udev->dev,
				"sendmsg failed!, retval %d for %zd\n",
				ret, txsize);
			usbip_event_add(&sdev->ud, SDEV_EVENT_ERROR_TCP);
			return -1;
		}

		usbip_dbg_stub_tx("send txdata\n");
		total_size += txsize;
	}

	spin_lock_irqsave(&sdev->priv_lock, flags);

	list_for_each_entry_safe(unlink, tmp, &sdev->unlink_free, list) {
		list_del(&unlink->list);
		kfree(unlink);
	}

	spin_unlock_irqrestore(&sdev->priv_lock, flags);

	return total_size;
}

Project: linux
File: stub_tx.c

static struct stub_priv *dequeue_from_priv_tx(struct stub_device *sdev)
{
	unsigned long flags;
	struct stub_priv *priv, *tmp;

	spin_lock_irqsave(&sdev->priv_lock, flags);

	list_for_each_entry_safe(priv, tmp, &sdev->priv_tx, list) {
		list_move_tail(&priv->list, &sdev->priv_free);
		spin_unlock_irqrestore(&sdev->priv_lock, flags);
		return priv;
	}

	spin_unlock_irqrestore(&sdev->priv_lock, flags);

	return NULL;
}

Project: linux
File: stub_tx.c

static int stub_send_ret_submit(struct stub_device *sdev)
{
	unsigned long flags;
	struct stub_priv *priv, *tmp;

	struct msghdr msg;
	size_t txsize;

	size_t total_size = 0;

	while ((priv = dequeue_from_priv_tx(sdev)) != NULL) {
		int ret;
		struct urb *urb = priv->urb;
		struct usbip_header pdu_header;
		struct usbip_iso_packet_descriptor *iso_buffer = NULL;
		struct kvec *iov = NULL;
		int iovnum = 0;

		txsize = 0;
		memset(&pdu_header, 0, sizeof(pdu_header));
		memset(&msg, 0, sizeof(msg));

		if (urb->actual_length > 0 && !urb->transfer_buffer) {
			dev_err(&sdev->udev->dev,
				"urb: actual_length %d transfer_buffer null\n",
				urb->actual_length);
			return -1;
		}

		if (usb_pipetype(urb->pipe) == PIPE_ISOCHRONOUS)
			iovnum = 2 + urb->number_of_packets;
		else
			iovnum = 2;

		iov = kcalloc(iovnum, sizeof(struct kvec), GFP_KERNEL);

		if (!iov) {
			usbip_event_add(&sdev->ud, SDEV_EVENT_ERROR_MALLOC);
			return -1;
		}

		iovnum = 0;

		/* 1. setup usbip_header */
		setup_ret_submit_pdu(&pdu_header, urb);
		usbip_dbg_stub_tx("setup txdata seqnum: %d urb: %p\n",
				  pdu_header.base.seqnum, urb);
		usbip_header_correct_endian(&pdu_header, 1);

		iov[iovnum].iov_base = &pdu_header;
		iov[iovnum].iov_len  = sizeof(pdu_header);
		iovnum++;
		txsize += sizeof(pdu_header);

		/* 2. setup transfer buffer */
		if (usb_pipein(urb->pipe) &&
		    usb_pipetype(urb->pipe) != PIPE_ISOCHRONOUS &&
		    urb->actual_length > 0) {
			iov[iovnum].iov_base = urb->transfer_buffer;
			iov[iovnum].iov_len  = urb->actual_length;
			iovnum++;
			txsize += urb->actual_length;
		} else if (usb_pipein(urb->pipe) &&
			   usb_pipetype(urb->pipe) == PIPE_ISOCHRONOUS) {
			/*
			 * For isochronous packets: actual length is the sum of
			 * the actual length of the individual, packets, but as
			 * the packet offsets are not changed there will be
			 * padding between the packets. To optimally use the
			 * bandwidth the padding is not transmitted.
			 */

			int i;

			for (i = 0; i < urb->number_of_packets; i++) {
				iov[iovnum].iov_base = urb->transfer_buffer +
					urb->iso_frame_desc[i].offset;
				iov[iovnum].iov_len =
					urb->iso_frame_desc[i].actual_length;
				iovnum++;
				txsize += urb->iso_frame_desc[i].actual_length;
			}

			if (txsize != sizeof(pdu_header) + urb->actual_length) {
				dev_err(&sdev->udev->dev,
					"actual length of urb %d does not match iso packet sizes %zu\n",
					urb->actual_length,
					txsize-sizeof(pdu_header));
				kfree(iov);
				usbip_event_add(&sdev->ud,
						SDEV_EVENT_ERROR_TCP);
			   return -1;
			}
		}

		/* 3. setup iso_packet_descriptor */
		if (usb_pipetype(urb->pipe) == PIPE_ISOCHRONOUS) {
			ssize_t len = 0;

			iso_buffer = usbip_alloc_iso_desc_pdu(urb, &len);
			if (!iso_buffer) {
				usbip_event_add(&sdev->ud,
						SDEV_EVENT_ERROR_MALLOC);
				kfree(iov);
				return -1;
			}

			iov[iovnum].iov_base = iso_buffer;
			iov[iovnum].iov_len  = len;
			txsize += len;
			iovnum++;
		}

		ret = kernel_sendmsg(sdev->ud.tcp_socket, &msg,
						iov,  iovnum, txsize);
		if (ret != txsize) {
			dev_err(&sdev->udev->dev,
				"sendmsg failed!, retval %d for %zd\n",
				ret, txsize);
			kfree(iov);
			kfree(iso_buffer);
			usbip_event_add(&sdev->ud, SDEV_EVENT_ERROR_TCP);
			return -1;
		}

		kfree(iov);
		kfree(iso_buffer);

		total_size += txsize;
	}

	spin_lock_irqsave(&sdev->priv_lock, flags);
	list_for_each_entry_safe(priv, tmp, &sdev->priv_free, list) {
		stub_free_priv_and_urb(priv);
	}
	spin_unlock_irqrestore(&sdev->priv_lock, flags);

	return total_size;
}

Project: linux
File: stub_tx.c

static struct stub_unlink *dequeue_from_unlink_tx(struct stub_device *sdev)
{
	unsigned long flags;
	struct stub_unlink *unlink, *tmp;

	spin_lock_irqsave(&sdev->priv_lock, flags);

	list_for_each_entry_safe(unlink, tmp, &sdev->unlink_tx, list) {
		list_move_tail(&unlink->list, &sdev->unlink_free);
		spin_unlock_irqrestore(&sdev->priv_lock, flags);
		return unlink;
	}

	spin_unlock_irqrestore(&sdev->priv_lock, flags);

	return NULL;
}

Project: linux
File: stub_tx.c

static inline void setup_base_pdu(struct usbip_header_basic *base,
				  __u32 command, __u32 seqnum)
{
	base->command	= command;
	base->seqnum	= seqnum;
	base->devid	= 0;
	base->ep	= 0;
	base->direction = 0;
}

Project: linux
File: stub_tx.c

void stub_complete(struct urb *urb)
{
	struct stub_priv *priv = (struct stub_priv *) urb->context;
	struct stub_device *sdev = priv->sdev;
	unsigned long flags;

	usbip_dbg_stub_tx("complete! status %d\n", urb->status);

	switch (urb->status) {
	case 0:
		/* OK */
		break;
	case -ENOENT:
		dev_info(&urb->dev->dev,
			 "stopped by a call to usb_kill_urb() because of cleaning up a virtual connection\n");
		return;
	case -ECONNRESET:
		dev_info(&urb->dev->dev,
			 "unlinked by a call to usb_unlink_urb()\n");
		break;
	case -EPIPE:
		dev_info(&urb->dev->dev, "endpoint %d is stalled\n",
			 usb_pipeendpoint(urb->pipe));
		break;
	case -ESHUTDOWN:
		dev_info(&urb->dev->dev, "device removed?\n");
		break;
	default:
		dev_info(&urb->dev->dev,
			 "urb completion with non-zero status %d\n",
			 urb->status);
		break;
	}

	/* link a urb to the queue of tx. */
	spin_lock_irqsave(&sdev->priv_lock, flags);
	if (sdev->ud.tcp_socket == NULL) {
		usbip_dbg_stub_tx("ignore urb for closed connection %p", urb);
		/* It will be freed in stub_device_cleanup_urbs(). */
	} else if (priv->unlinking) {
		stub_enqueue_ret_unlink(sdev, priv->seqnum, urb->status);
		stub_free_priv_and_urb(priv);
	} else {
		list_move_tail(&priv->list, &sdev->priv_tx);
	}
	spin_unlock_irqrestore(&sdev->priv_lock, flags);

	/* wake up tx_thread */
	wake_up(&sdev->tx_waitq);
}

Project: linux
File: stub_tx.c

int stub_tx_loop(void *data)
{
	struct usbip_device *ud = data;
	struct stub_device *sdev = container_of(ud, struct stub_device, ud);

	while (!kthread_should_stop()) {
		if (usbip_event_happened(ud))
			break;

		/*
		 * send_ret_submit comes earlier than send_ret_unlink.  stub_rx
		 * looks at only priv_init queue. If the completion of a URB is
		 * earlier than the receive of CMD_UNLINK, priv is moved to
		 * priv_tx queue and stub_rx does not find the target priv. In
		 * this case, vhci_rx receives the result of the submit request
		 * and then receives the result of the unlink request. The
		 * result of the submit is given back to the usbcore as the
		 * completion of the unlink request. The request of the
		 * unlink is ignored. This is ok because a driver who calls
		 * usb_unlink_urb() understands the unlink was too late by
		 * getting the status of the given-backed URB which has the
		 * status of usb_submit_urb().
		 */
		if (stub_send_ret_submit(sdev) < 0)
			break;

		if (stub_send_ret_unlink(sdev) < 0)
			break;

		wait_event_interruptible(sdev->tx_waitq,
					 (!list_empty(&sdev->priv_tx) ||
					  !list_empty(&sdev->unlink_tx) ||
					  kthread_should_stop()));
	}

	return 0;
}

Project: linux
File: stub_tx.c

void stub_enqueue_ret_unlink(struct stub_device *sdev, __u32 seqnum,
			     __u32 status)
{
	struct stub_unlink *unlink;

	unlink = kzalloc(sizeof(struct stub_unlink), GFP_ATOMIC);
	if (!unlink) {
		usbip_event_add(&sdev->ud, VDEV_EVENT_ERROR_MALLOC);
		return;
	}

	unlink->seqnum = seqnum;
	unlink->status = status;

	list_add_tail(&unlink->list, &sdev->unlink_tx);
}

Project: linux
File: stub_tx.c

static void stub_free_priv_and_urb(struct stub_priv *priv)
{
	struct urb *urb = priv->urb;

	kfree(urb->setup_packet);
	urb->setup_packet = NULL;

	kfree(urb->transfer_buffer);
	urb->transfer_buffer = NULL;

	list_del(&priv->list);
	kmem_cache_free(stub_priv_cache, priv);
	usb_free_urb(urb);
}

Project: linux
File: stub_tx.c

static void setup_ret_submit_pdu(struct usbip_header *rpdu, struct urb *urb)
{
	struct stub_priv *priv = (struct stub_priv *) urb->context;

	setup_base_pdu(&rpdu->base, USBIP_RET_SUBMIT, priv->seqnum);
	usbip_pack_pdu(rpdu, urb, USBIP_RET_SUBMIT, 1);
}