From 27a24e029b48f738d0b2534aebe7c7f06e1fac67 Mon Sep 17 00:00:00 2001
From: Shuah Khan <shuahkh@osg.samsung.com>
Date: Thu, 7 Dec 2017 14:16:48 -0700
Subject: [PATCH] usbip: fix stub_rx: harden CMD_SUBMIT path to handle
 malicious input
Git-commit: c6688ef9f29762e65bce325ef4acd6c675806366
Patch-mainline: v4.15-rc4
References: bsc#1078672 CVE-2017-16913

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@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>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/usb/usbip/stub_rx.c | 37 ++++++++++++++++++++++++++++++++-----
 1 file changed, 32 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/usbip/stub_rx.c b/drivers/usb/usbip/stub_rx.c
index 191b176ffedf..8dbd8bf838c3 100644
--- a/drivers/usb/usbip/stub_rx.c
+++ b/drivers/usb/usbip/stub_rx.c
@@ -336,11 +336,13 @@ 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 (epnum < 0 || epnum > 15)
 		goto err_ret;
@@ -353,6 +355,15 @@ static int get_pipe(struct stub_device *sdev, int epnum, int dir)
 		goto err_ret;
 
 	epd = &ep->desc;
+
+	/* validate transfer_buffer_length */
+	if (pdu->u.cmd_submit.transfer_buffer_length > INT_MAX) {
+		dev_err(&sdev->udev->dev,
+			"CMD_SUBMIT: -EMSGSIZE transfer_buffer_length %d\n",
+			pdu->u.cmd_submit.transfer_buffer_length);
+		return -1;
+	}
+
 	if (usb_endpoint_xfer_control(epd)) {
 		if (dir == USBIP_DIR_OUT)
 			return usb_sndctrlpipe(udev, epnum);
@@ -375,6 +386,21 @@ 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;
+
+		maxp = usb_endpoint_maxp(epd);
+		maxp *= usb_endpoint_maxp_mult(epd);
+		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
@@ -382,8 +408,8 @@ static int get_pipe(struct stub_device *sdev, int epnum, int dir)
 
 err_ret:
 	/* NOT REACHED */
-	dev_err(&sdev->udev->dev, "get pipe() invalid epnum %d\n", epnum);
-	return 0;
+	dev_err(&sdev->udev->dev, "CMD_SUBMIT: invalid epnum %d\n", epnum);
+	return -1;
 }
 
 static void masking_bogus_flags(struct urb *urb)
@@ -447,7 +473,7 @@ 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);
 
 	if (pipe == -1)
 		return;
@@ -466,7 +492,8 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 	}
 
 	/* allocate urb transfer buffer, if needed */
-	if (pdu->u.cmd_submit.transfer_buffer_length > 0) {
+	if (pdu->u.cmd_submit.transfer_buffer_length > 0 &&
+	    pdu->u.cmd_submit.transfer_buffer_length <= INT_MAX) {
 		priv->urb->transfer_buffer =
 			kzalloc(pdu->u.cmd_submit.transfer_buffer_length,
 				GFP_KERNEL);
-- 
2.13.6