linux-kernel - [PATCH 4.4] usbip: prevent vhci_hcd driver from leaking a socket pointer address

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Message-Id: <20180124023404.32217-1-shuahkh@osg.samsung.com>
Date:   Tue, 23 Jan 2018 19:34:04 -0700
From:   Shuah Khan <shuahkh@....samsung.com>
To:     valentina.manea.m@...il.com, shuah@...nel.org,
        gregkh@...uxfoundation.org
Cc:     Shuah Khan <shuahkh@....samsung.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH 4.4] usbip: prevent vhci_hcd driver from leaking a socket pointer address

commit 2f2d0088eb93 ("usbip: prevent vhci_hcd driver from leaking a
socket pointer address")

When a client has a USB device attached over IP, the vhci_hcd driver is
locally leaking a socket pointer address via the

/sys/devices/platform/vhci_hcd/status file (world-readable) and in debug
output when "usbip --debug port" is run.

Fix it to not leak. The socket pointer address is not used at the moment
and it was made visible as a convenient way to find IP address from
socket pointer address by looking up /proc/net/{tcp,tcp6}.

As this opens a security hole, the fix replaces socket pointer address
with sockfd.

Reported-by: Secunia Research <vuln@...unia.com>
Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
---
 drivers/usb/usbip/usbip_common.h     |  1 +
 drivers/usb/usbip/vhci_sysfs.c       | 25 +++++++++++++++----------
 tools/usb/usbip/libsrc/vhci_driver.c |  8 ++++----
 3 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/drivers/usb/usbip/usbip_common.h b/drivers/usb/usbip/usbip_common.h
index 86b08475c254..f875ccaa55f9 100644
--- a/drivers/usb/usbip/usbip_common.h
+++ b/drivers/usb/usbip/usbip_common.h
@@ -261,6 +261,7 @@ struct usbip_device {
 	/* lock for status */
 	spinlock_t lock;
 
+	int sockfd;
 	struct socket *tcp_socket;
 
 	struct task_struct *tcp_rx;
diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
index 211f43f67ea2..84c21c4ccf46 100644
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -39,16 +39,20 @@ static ssize_t status_show(struct device *dev, struct device_attribute *attr,
 
 	/*
 	 * output example:
-	 * prt sta spd dev socket           local_busid
-	 * 000 004 000 000         c5a7bb80 1-2.3
-	 * 001 004 000 000         d8cee980 2-3.4
+	 * port sta spd dev      sockfd local_busid
+	 * 0000 004 000 00000000 000003 1-2.3
+	 * 0001 004 000 00000000 000004 2-3.4
 	 *
-	 * IP address can be retrieved from a socket pointer address by looking
-	 * up /proc/net/{tcp,tcp6}. Also, a userland program may remember a
-	 * port number and its peer IP address.
+	 * Output includes socket fd instead of socket pointer address to
+	 * avoid leaking kernel memory address in:
+	 *	/sys/devices/platform/vhci_hcd.0/status and in debug output.
+	 * The socket pointer address is not used at the moment and it was
+	 * made visible as a convenient way to find IP address from socket
+	 * pointer address by looking up /proc/net/{tcp,tcp6}. As this opens
+	 * a security hole, the change is made to use sockfd instead.
 	 */
 	out += sprintf(out,
-		       "prt sta spd bus dev socket           local_busid\n");
+		       "prt sta spd bus dev sockfd local_busid\n");
 
 	for (i = 0; i < VHCI_NPORTS; i++) {
 		struct vhci_device *vdev = port_to_vdev(i);
@@ -60,11 +64,11 @@ static ssize_t status_show(struct device *dev, struct device_attribute *attr,
 			out += sprintf(out, "%03u %08x ",
 				       vdev->speed, vdev->devid);
 			out += sprintf(out, "%16p ", vdev->ud.tcp_socket);
+			out += sprintf(out, "%06u", vdev->ud.sockfd);
 			out += sprintf(out, "%s", dev_name(&vdev->udev->dev));
 
-		} else {
-			out += sprintf(out, "000 000 000 0000000000000000 0-0");
-		}
+		} else
+			out += sprintf(out, "000 000 000 000000 0-0");
 
 		out += sprintf(out, "\n");
 		spin_unlock(&vdev->ud.lock);
@@ -223,6 +227,7 @@ static ssize_t store_attach(struct device *dev, struct device_attribute *attr,
 
 	vdev->devid         = devid;
 	vdev->speed         = speed;
+	vdev->ud.sockfd     = sockfd;
 	vdev->ud.tcp_socket = socket;
 	vdev->ud.status     = VDEV_ST_NOTASSIGNED;
 
diff --git a/tools/usb/usbip/libsrc/vhci_driver.c b/tools/usb/usbip/libsrc/vhci_driver.c
index ad9204773533..1274f326242c 100644
--- a/tools/usb/usbip/libsrc/vhci_driver.c
+++ b/tools/usb/usbip/libsrc/vhci_driver.c
@@ -55,12 +55,12 @@ static int parse_status(const char *value)
 
 	while (*c != '\0') {
 		int port, status, speed, devid;
-		unsigned long socket;
+		int sockfd;
 		char lbusid[SYSFS_BUS_ID_SIZE];
 
-		ret = sscanf(c, "%d %d %d %x %lx %31s\n",
+		ret = sscanf(c, "%d %d %d %x %u %31s\n",
 				&port, &status, &speed,
-				&devid, &socket, lbusid);
+				&devid, &sockfd, lbusid);
 
 		if (ret < 5) {
 			dbg("sscanf failed: %d", ret);
@@ -69,7 +69,7 @@ static int parse_status(const char *value)
 
 		dbg("port %d status %d speed %d devid %x",
 				port, status, speed, devid);
-		dbg("socket %lx lbusid %s", socket, lbusid);
+		dbg("sockfd %u lbusid %s", sockfd, lbusid);
 
 
 		/* if a device is connected, look at it */
-- 
2.14.1