usb: devio: Add ioctl to disallow detaching kernel USB drivers.
The new USBDEVFS_DROP_PRIVILEGES ioctl allows a process to voluntarily
relinquish the ability to issue other ioctls that may interfere with
other processes and drivers that have claimed an interface on the
device.
This commit also includes a simple utility to be able to test the
ioctl, located at Documentation/usb/usbdevfs-drop-permissions.c
Example (with qemu-kvm's input device):
$ lsusb
...
Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd
$ usb-devices
...
C: #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr=100mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=02 Driver=usbhid
$ sudo ./usbdevfs-drop-permissions /dev/bus/usb/001/002
OK: privileges dropped!
Available options:
[0] Exit now
[1] Reset device. Should fail if device is in use
[2] Claim 4 interfaces. Should succeed where not in use
[3] Narrow interface permission mask
Which option shall I run?: 1
ERROR: USBDEVFS_RESET failed! (1 - Operation not permitted)
Which test shall I run next?: 2
ERROR claiming if 0 (1 - Operation not permitted)
ERROR claiming if 1 (1 - Operation not permitted)
ERROR claiming if 2 (1 - Operation not permitted)
ERROR claiming if 3 (1 - Operation not permitted)
Which test shall I run next?: 0
After unbinding usbhid:
$ usb-devices
...
I: If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=02 Driver=(none)
$ sudo ./usbdevfs-drop-permissions /dev/bus/usb/001/002
...
Which option shall I run?: 2
OK: claimed if 0
ERROR claiming if 1 (1 - Operation not permitted)
ERROR claiming if 2 (1 - Operation not permitted)
ERROR claiming if 3 (1 - Operation not permitted)
Which test shall I run next?: 1
OK: USBDEVFS_RESET succeeded
Which test shall I run next?: 0
After unbinding usbhid and restricting the mask:
$ sudo ./usbdevfs-drop-permissions /dev/bus/usb/001/002
...
Which option shall I run?: 3
Insert new mask: 0
OK: privileges dropped!
Which test shall I run next?: 2
ERROR claiming if 0 (1 - Operation not permitted)
ERROR claiming if 1 (1 - Operation not permitted)
ERROR claiming if 2 (1 - Operation not permitted)
ERROR claiming if 3 (1 - Operation not permitted)
Signed-off-by: Reilly Grant <reillyg@chromium.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Emilio López <emilio.lopez@collabora.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 39da166..52c4461 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -79,6 +79,8 @@
unsigned long ifclaimed;
u32 secid;
u32 disabled_bulk_eps;
+ bool privileges_dropped;
+ unsigned long interface_allowed_mask;
};
struct usb_memory {
@@ -748,6 +750,10 @@
if (test_bit(ifnum, &ps->ifclaimed))
return 0;
+ if (ps->privileges_dropped &&
+ !test_bit(ifnum, &ps->interface_allowed_mask))
+ return -EACCES;
+
intf = usb_ifnum_to_if(dev, ifnum);
if (!intf)
err = -ENOENT;
@@ -985,7 +991,7 @@
int ret;
ret = -ENOMEM;
- ps = kmalloc(sizeof(struct usb_dev_state), GFP_KERNEL);
+ ps = kzalloc(sizeof(struct usb_dev_state), GFP_KERNEL);
if (!ps)
goto out_free_ps;
@@ -1013,17 +1019,15 @@
ps->dev = dev;
ps->file = file;
+ ps->interface_allowed_mask = 0xFFFFFFFF; /* 32 bits */
spin_lock_init(&ps->lock);
INIT_LIST_HEAD(&ps->list);
INIT_LIST_HEAD(&ps->async_pending);
INIT_LIST_HEAD(&ps->async_completed);
INIT_LIST_HEAD(&ps->memory_list);
init_waitqueue_head(&ps->wait);
- ps->discsignr = 0;
ps->disc_pid = get_pid(task_pid(current));
ps->cred = get_current_cred();
- ps->disccontext = NULL;
- ps->ifclaimed = 0;
security_task_getsecid(current, &ps->secid);
smp_wmb();
list_add_tail(&ps->list, &dev->filelist);
@@ -1324,6 +1328,28 @@
static int proc_resetdevice(struct usb_dev_state *ps)
{
+ struct usb_host_config *actconfig = ps->dev->actconfig;
+ struct usb_interface *interface;
+ int i, number;
+
+ /* Don't allow a device reset if the process has dropped the
+ * privilege to do such things and any of the interfaces are
+ * currently claimed.
+ */
+ if (ps->privileges_dropped && actconfig) {
+ for (i = 0; i < actconfig->desc.bNumInterfaces; ++i) {
+ interface = actconfig->interface[i];
+ number = interface->cur_altsetting->desc.bInterfaceNumber;
+ if (usb_interface_claimed(interface) &&
+ !test_bit(number, &ps->ifclaimed)) {
+ dev_warn(&ps->dev->dev,
+ "usbfs: interface %d claimed by %s while '%s' resets device\n",
+ number, interface->dev.driver->name, current->comm);
+ return -EACCES;
+ }
+ }
+ }
+
return usb_reset_device(ps->dev);
}
@@ -2090,6 +2116,9 @@
struct usb_interface *intf = NULL;
struct usb_driver *driver = NULL;
+ if (ps->privileges_dropped)
+ return -EACCES;
+
/* alloc buffer */
size = _IOC_SIZE(ctl->ioctl_code);
if (size > 0) {
@@ -2215,7 +2244,8 @@
__u32 caps;
caps = USBDEVFS_CAP_ZERO_PACKET | USBDEVFS_CAP_NO_PACKET_SIZE_LIM |
- USBDEVFS_CAP_REAP_AFTER_DISCONNECT | USBDEVFS_CAP_MMAP;
+ USBDEVFS_CAP_REAP_AFTER_DISCONNECT | USBDEVFS_CAP_MMAP |
+ USBDEVFS_CAP_DROP_PRIVILEGES;
if (!ps->dev->bus->no_stop_on_short)
caps |= USBDEVFS_CAP_BULK_CONTINUATION;
if (ps->dev->bus->sg_tablesize)
@@ -2242,6 +2272,9 @@
if (intf->dev.driver) {
struct usb_driver *driver = to_usb_driver(intf->dev.driver);
+ if (ps->privileges_dropped)
+ return -EACCES;
+
if ((dc.flags & USBDEVFS_DISCONNECT_CLAIM_IF_DRIVER) &&
strncmp(dc.driver, intf->dev.driver->name,
sizeof(dc.driver)) != 0)
@@ -2298,6 +2331,23 @@
return r;
}
+static int proc_drop_privileges(struct usb_dev_state *ps, void __user *arg)
+{
+ u32 data;
+
+ if (copy_from_user(&data, arg, sizeof(data)))
+ return -EFAULT;
+
+ /* This is an one way operation. Once privileges are
+ * dropped, you cannot regain them. You may however reissue
+ * this ioctl to shrink the allowed interfaces mask.
+ */
+ ps->interface_allowed_mask &= data;
+ ps->privileges_dropped = true;
+
+ return 0;
+}
+
/*
* NOTE: All requests here that have interface numbers as parameters
* are assuming that somehow the configuration has been prevented from
@@ -2486,6 +2536,9 @@
case USBDEVFS_FREE_STREAMS:
ret = proc_free_streams(ps, p);
break;
+ case USBDEVFS_DROP_PRIVILEGES:
+ ret = proc_drop_privileges(ps, p);
+ break;
}
done: