From a0d6ec88090d7b1b008429c44532a388e29bb1bd Mon Sep 17 00:00:00 2001
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Fri, 18 May 2018 20:13:42 -0500
Subject: [PATCH] usbip: vhci_sysfs: fix potential Spectre v1
Git-commit: a0d6ec88090d7b1b008429c44532a388e29bb1bd
Patch-mainline: v4.18-rc1
References: bsc#1051510

pdev_nr and rhport can be controlled by user-space, hence leading to
a potential exploitation of the Spectre variant 1 vulnerability.

This issue was detected with the help of Smatch:
drivers/usb/usbip/vhci_sysfs.c:238 detach_store() warn: potential spectre issue 'vhcis'
drivers/usb/usbip/vhci_sysfs.c:328 attach_store() warn: potential spectre issue 'vhcis'
drivers/usb/usbip/vhci_sysfs.c:338 attach_store() warn: potential spectre issue 'vhci->vhci_hcd_ss->vdev'
drivers/usb/usbip/vhci_sysfs.c:340 attach_store() warn: potential spectre issue 'vhci->vhci_hcd_hs->vdev'

Fix this by sanitizing pdev_nr and rhport before using them to index
vhcis and vhci->vhci_hcd_ss->vdev respectively.

Notice that given that speculation windows are large, the policy is
to kill the speculation on the first load and not worry if it can be
completed with a dependent load/store [1].

[1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2

Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/usb/usbip/vhci_sysfs.c |   24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -24,6 +24,9 @@
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 
+/* Hardening for Spectre-v1 */
+#include <linux/nospec.h>
+
 #include "usbip_common.h"
 #include "vhci.h"
 
@@ -182,16 +185,20 @@ static int vhci_port_disconnect(struct v
 	return 0;
 }
 
-static int valid_port(__u32 pdev_nr, __u32 rhport)
+static int valid_port(__u32 *pdev_nr, __u32 *rhport)
 {
-	if (pdev_nr >= vhci_num_controllers) {
-		pr_err("pdev %u\n", pdev_nr);
+	if (*pdev_nr >= vhci_num_controllers) {
+		pr_err("pdev %u\n", *pdev_nr);
 		return 0;
 	}
-	if (rhport >= VHCI_HC_PORTS) {
-		pr_err("rhport %u\n", rhport);
+	*pdev_nr = array_index_nospec(*pdev_nr, vhci_num_controllers);
+
+	if (*rhport >= VHCI_HC_PORTS) {
+		pr_err("rhport %u\n", *rhport);
 		return 0;
 	}
+	*rhport = array_index_nospec(*rhport, VHCI_HC_PORTS);
+
 	return 1;
 }
 
@@ -208,7 +215,7 @@ static ssize_t detach_store(struct devic
 	pdev_nr = port_to_pdev_nr(port);
 	rhport = port_to_rhport(port);
 
-	if (!valid_port(pdev_nr, rhport))
+	if (!valid_port(&pdev_nr, &rhport))
 		return -EINVAL;
 
 	hcd = platform_get_drvdata(*(vhci_pdevs + pdev_nr));
@@ -227,7 +234,8 @@ static ssize_t detach_store(struct devic
 }
 static DEVICE_ATTR_WO(detach);
 
-static int valid_args(__u32 pdev_nr, __u32 rhport, enum usb_device_speed speed)
+static int valid_args(__u32 *pdev_nr, __u32 *rhport,
+		      enum usb_device_speed speed)
 {
 	if (!valid_port(pdev_nr, rhport)) {
 		return 0;
@@ -289,7 +297,7 @@ static ssize_t attach_store(struct devic
 			     sockfd, devid, speed);
 
 	/* check received parameters */
-	if (!valid_args(pdev_nr, rhport, speed))
+	if (!valid_args(&pdev_nr, &rhport, speed))
 		return -EINVAL;
 
 	hcd = platform_get_drvdata(*(vhci_pdevs + pdev_nr));