[PATCH 4.14 11/36] usbip: vhci_sysfs: fix potential Spectre v1

Greg Kroah-Hartman
2018-06-14T14:31:32Z

From: Gustavo A. R. Silva <gustavo@embeddedor.com>

commit a0d6ec88090d7b1b008429c44532a388e29bb1bd upstream.

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>

---
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"

@@ -219,16 +222,20 @@ 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;
}

@@ -246,7 +253,7 @@ static ssize_t store_detach(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(vhcis[pdev_nr].pdev);
@@ -272,7 +279,8 @@ static ssize_t store_detach(struct devic
}
static DEVICE_ATTR(detach, S_IWUSR, NULL, store_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;
@@ -336,7 +344,7 @@ static ssize_t store_attach(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(vhcis[pdev_nr].pdev);