linux-kernel - [PATCH 3/4] usbip: prevent vhci_hcd driver from leaking a socket pointer address

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Message-Id: <96d723665e9feda55f38a2d4d5cd23b4201cb70d.1512672005.git.shuahkh@osg.samsung.com>
Date:   Thu,  7 Dec 2017 14:16:49 -0700
From:   Shuah Khan <shuahkh@....samsung.com>
To:     shuah@...nel.org, valentina.manea.m@...il.com,
        gregkh@...uxfoundation.org
Cc:     Shuah Khan <shuahkh@....samsung.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 3/4] 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.

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, 21 insertions(+), 13 deletions(-)

diff --git a/drivers/usb/usbip/usbip_common.h b/drivers/usb/usbip/usbip_common.h
index e5de35c8c505..473fb8a87289 100644
--- a/drivers/usb/usbip/usbip_common.h
+++ b/drivers/usb/usbip/usbip_common.h
@@ -256,6 +256,7 @@ 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 e78f7472cac4..091f76b7196d 100644
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -17,15 +17,20 @@
 
 /*
  * output example:
- * hub port sta spd dev      socket           local_busid
- * hs  0000 004 000 00000000         c5a7bb80 1-2.3
+ * hub port sta spd dev       sockfd    local_busid
+ * hs  0000 004 000 00000000  3         1-2.3
  * ................................................
- * ss  0008 004 000 00000000         d8cee980 2-3.4
+ * ss  0008 004 000 00000000  4         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.
+ *
  */
 static void port_show_vhci(char **out, int hub, int port, struct vhci_device *vdev)
 {
@@ -39,8 +44,8 @@ static void port_show_vhci(char **out, int hub, int port, struct vhci_device *vd
 	if (vdev->ud.status == VDEV_ST_USED) {
 		*out += sprintf(*out, "%03u %08x ",
 				      vdev->speed, vdev->devid);
-		*out += sprintf(*out, "%16p %s",
-				      vdev->ud.tcp_socket,
+		*out += sprintf(*out, "%u %s",
+				      vdev->ud.sockfd,
 				      dev_name(&vdev->udev->dev));
 
 	} else {
@@ -160,7 +165,8 @@ static ssize_t nports_show(struct device *dev, struct device_attribute *attr,
 	char *s = out;
 
 	/*
-	 * Half the ports are for SPEED_HIGH and half for SPEED_SUPER, thus the * 2.
+	 * Half the ports are for SPEED_HIGH and half for SPEED_SUPER,
+	 * thus the * 2.
 	 */
 	out += sprintf(out, "%d\n", VHCI_PORTS * vhci_num_controllers);
 	return out - s;
@@ -366,6 +372,7 @@ 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 8a1cd1616de4..d1fc0f9f00fb 100644
--- a/tools/usb/usbip/libsrc/vhci_driver.c
+++ b/tools/usb/usbip/libsrc/vhci_driver.c
@@ -50,14 +50,14 @@ 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];
 		struct usbip_imported_device *idev;
 		char hub[3];
 
-		ret = sscanf(c, "%2s  %d %d %d %x %lx %31s\n",
+		ret = sscanf(c, "%2s  %d %d %d %x %u %31s\n",
 				hub, &port, &status, &speed,
-				&devid, &socket, lbusid);
+				&devid, &sockfd, lbusid);
 
 		if (ret < 5) {
 			dbg("sscanf failed: %d", ret);
@@ -66,7 +66,7 @@ static int parse_status(const char *value)
 
 		dbg("hub %s port %d status %d speed %d devid %x",
 				hub, 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 */
 		idev = &vhci_driver->idev[port];
-- 
2.14.1