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: sta...@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gust...@embeddedor.com>
---
Changes in v3:
- Pass the addresses of pdev_nr and rhport into valid_port and
valid_args.
Changes in v2:
- Place the barriers into valid_port.
drivers/usb/usbip/vhci_sysfs.c | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)
diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
index 4880838..be37aec 100644
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -10,6 +10,9 @@
#include <linux/platform_device.h>
#include <linux/slab.h>
+/* Hardening for Spectre-v1 */
+#include <linux/nospec.h>
+
#include "usbip_common.h"
#include "vhci.h"
@@ -205,16 +208,20 @@ static int vhci_port_disconnect(struct vhci_hcd *vhci_hcd, __u32 rhport)
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;
}
@@ -232,7 +239,7 @@ static ssize_t detach_store(struct device *dev, struct device_attribute *attr,
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);
@@ -258,7 +265,8 @@ static ssize_t detach_store(struct device *dev, struct
device_attribute *attr,
}
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;
@@ -322,7 +330,7 @@ static ssize_t attach_store(struct device *dev, struct
device_attribute *attr,
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);
