From: Reilly Grant <reil...@chromium.org>
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.
Signed-off-by: Reilly Grant <reil...@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorg...@chromium.org>
Reviewed-by: Kees Cook <keesc...@chromium.org>
[emilio.lopez: fix build for v4.4-rc2 and adjust patch title prefix]
Signed-off-by: Emilio López <emilio.lo...@collabora.co.uk>
---
drivers/usb/core/devio.c | 50 +++++++++++++++++++++++++++++++++++----
include/uapi/linux/usbdevice_fs.h | 1 +
2 files changed, 47 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 38ae877c..a5ccc50 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -77,6 +77,7 @@ struct usb_dev_state {
unsigned long ifclaimed;
u32 secid;
u32 disabled_bulk_eps;
+ bool privileges_dropped;
};
struct async {
@@ -878,7 +879,7 @@ static int usbdev_open(struct inode *inode, struct file
*file)
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;
@@ -911,11 +912,8 @@ static int usbdev_open(struct inode *inode, struct file
*file)
INIT_LIST_HEAD(&ps->async_pending);
INIT_LIST_HEAD(&ps->async_completed);
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);
@@ -1215,6 +1213,35 @@ static int proc_connectinfo(struct usb_dev_state *ps,
void __user *arg)
static int proc_resetdevice(struct usb_dev_state *ps)
{
+ if (ps->privileges_dropped) {
+ struct usb_host_config *actconfig = ps->dev->actconfig;
+
+ /* Don't touch the device if any interfaces are claimed. It
+ * could interfere with other drivers' operations and this
+ * process has dropped its privileges to do such things.
+ */
+ if (actconfig) {
+ int i;
+
+ for (i = 0; i < actconfig->desc.bNumInterfaces; ++i) {
+ if (usb_interface_claimed(
+ actconfig->interface[i])) {
+ dev_warn(&ps->dev->dev,
+ "usbfs: interface %d claimed by"
+ " %s while '%s'"
+ " resets device\n",
+ actconfig->interface[i]
+ ->cur_altsetting
+ ->desc.bInterfaceNumber,
+ actconfig->interface[i]
+ ->dev.driver->name,
+ current->comm);
+ return -EACCES;
+ }
+ }
+ }
+ }
+
return usb_reset_device(ps->dev);
}
@@ -1922,6 +1949,9 @@ static int proc_ioctl(struct usb_dev_state *ps, struct
usbdevfs_ioctl *ctl)
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) {
@@ -2084,6 +2114,9 @@ static int proc_disconnect_claim(struct usb_dev_state
*ps, void __user *arg)
sizeof(dc.driver)) == 0)
return -EBUSY;
+ if (ps->privileges_dropped)
+ return -EACCES;
+
dev_dbg(&intf->dev, "disconnect by usbfs\n");
usb_driver_release_interface(driver, intf);
}
@@ -2130,6 +2163,12 @@ static int proc_free_streams(struct usb_dev_state *ps,
void __user *arg)
return r;
}
+static int proc_drop_privileges(struct usb_dev_state *ps)
+{
+ 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
@@ -2318,6 +2357,9 @@ static long usbdev_do_ioctl(struct file *file, unsigned
int cmd,
case USBDEVFS_FREE_STREAMS:
ret = proc_free_streams(ps, p);
break;
+ case USBDEVFS_DROP_PRIVILEGES:
+ ret = proc_drop_privileges(ps);
+ break;
}
done:
diff --git a/include/uapi/linux/usbdevice_fs.h
b/include/uapi/linux/usbdevice_fs.h
index 019ba1e..99c296b 100644
--- a/include/uapi/linux/usbdevice_fs.h
+++ b/include/uapi/linux/usbdevice_fs.h
@@ -187,5 +187,6 @@ struct usbdevfs_streams {
#define USBDEVFS_DISCONNECT_CLAIM _IOR('U', 27, struct
usbdevfs_disconnect_claim)
#define USBDEVFS_ALLOC_STREAMS _IOR('U', 28, struct usbdevfs_streams)
#define USBDEVFS_FREE_STREAMS _IOR('U', 29, struct usbdevfs_streams)
+#define USBDEVFS_DROP_PRIVILEGES _IO('U', 30)
#endif /* _UAPI_LINUX_USBDEVICE_FS_H */
--
2.5.0
--
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