[SRU][Trusty][PATCH 1/1] usbip: fix stub_rx: harden CMD_SUBMIT path to handle malicious input

[Kleber Sacilotto de Souza]

From: Shuah Khan <shuahkh at osg.samsung.com>

commit c6688ef9f29762e65bce325ef4acd6c675806366 upstream.

Harden CMD_SUBMIT path to handle malicious input that could trigger
large memory allocations. Add checks to validate transfer_buffer_length
and number_of_packets to protect against bad input requesting for
unbounded memory allocations. Validate early in get_pipe() and return
failure.

Reported-by: Secunia Research <vuln at secunia.com>
Signed-off-by: Shuah Khan <shuahkh at osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>

CVE-2017-16913
(backported from commit eebf31529012289ec20fea84e4e6fd188176be13 linux-stable)
[ klebers: adjusted the file path, the usbip is still under staging on
  kernel 3.13, and some minor context adjustment. ]
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
---
 drivers/staging/usbip/stub_rx.c | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/usbip/stub_rx.c b/drivers/staging/usbip/stub_rx.c
index db48a789d308..d9262ad46d42 100644
--- a/drivers/staging/usbip/stub_rx.c
+++ b/drivers/staging/usbip/stub_rx.c
@@ -349,11 +349,13 @@ static struct stub_priv *stub_priv_alloc(struct stub_device *sdev,
 	return priv;
 }
 
-static int get_pipe(struct stub_device *sdev, int epnum, int dir)
+static int get_pipe(struct stub_device *sdev, struct usbip_header *pdu)
 {
 	struct usb_device *udev = sdev->udev;
 	struct usb_host_endpoint *ep;
 	struct usb_endpoint_descriptor *epd = NULL;
+	int epnum = pdu->base.ep;
+	int dir = pdu->base.direction;
 
 	if (dir == USBIP_DIR_IN)
 		ep = udev->ep_in[epnum & 0x7f];
@@ -366,6 +368,7 @@ static int get_pipe(struct stub_device *sdev, int epnum, int dir)
 	}
 
 	epd = &ep->desc;
+
 	if (usb_endpoint_xfer_control(epd)) {
 		if (dir == USBIP_DIR_OUT)
 			return usb_sndctrlpipe(udev, epnum);
@@ -388,6 +391,27 @@ static int get_pipe(struct stub_device *sdev, int epnum, int dir)
 	}
 
 	if (usb_endpoint_xfer_isoc(epd)) {
+		/* validate packet size and number of packets */
+		unsigned int maxp, packets, bytes;
+
+#define USB_EP_MAXP_MULT_SHIFT  11
+#define USB_EP_MAXP_MULT_MASK   (3 << USB_EP_MAXP_MULT_SHIFT)
+#define USB_EP_MAXP_MULT(m) \
+	(((m) & USB_EP_MAXP_MULT_MASK) >> USB_EP_MAXP_MULT_SHIFT)
+
+		maxp = usb_endpoint_maxp(epd);
+		maxp *= (USB_EP_MAXP_MULT(
+				__le16_to_cpu(epd->wMaxPacketSize)) + 1);
+		bytes = pdu->u.cmd_submit.transfer_buffer_length;
+		packets = DIV_ROUND_UP(bytes, maxp);
+
+		if (pdu->u.cmd_submit.number_of_packets < 0 ||
+		    pdu->u.cmd_submit.number_of_packets > packets) {
+			dev_err(&sdev->udev->dev,
+				"CMD_SUBMIT: isoc invalid num packets %d\n",
+				pdu->u.cmd_submit.number_of_packets);
+			return -1;
+		}
 		if (dir == USBIP_DIR_OUT)
 			return usb_sndisocpipe(udev, epnum);
 		else
@@ -395,7 +419,7 @@ static int get_pipe(struct stub_device *sdev, int epnum, int dir)
 	}
 
 	/* NOT REACHED */
-	dev_err(&sdev->interface->dev, "get pipe, epnum %d\n", epnum);
+	dev_err(&sdev->interface->dev, "CMD_SUBMIT: invalid epnum %d\n", epnum);
 	return 0;
 }
 
@@ -460,7 +484,7 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 	struct stub_priv *priv;
 	struct usbip_device *ud = &sdev->ud;
 	struct usb_device *udev = sdev->udev;
-	int pipe = get_pipe(sdev, pdu->base.ep, pdu->base.direction);
+	int pipe = get_pipe(sdev, pdu);
 
 	priv = stub_priv_alloc(sdev, pdu);
 	if (!priv)
-- 
2.17.1