From d883f52e1f6d2eca8378e3795f333c1396943873 Mon Sep 17 00:00:00 2001 From: Reilly Grant Date: Sun, 21 Feb 2016 18:38:01 -0300 Subject: usb: devio: Add ioctl to disallow detaching kernel USB drivers. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Acked-by: Alan Stern Signed-off-by: Emilio López Signed-off-by: Greg Kroah-Hartman --- Documentation/DocBook/usb.tmpl | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'Documentation/DocBook') diff --git a/Documentation/DocBook/usb.tmpl b/Documentation/DocBook/usb.tmpl index 4cd5b2cd0f3d..bc776be0f19c 100644 --- a/Documentation/DocBook/usb.tmpl +++ b/Documentation/DocBook/usb.tmpl @@ -732,6 +732,18 @@ usbdev_ioctl (int fd, int ifno, unsigned request, void *param) or SET_INTERFACE. + USBDEVFS_DROP_PRIVILEGES + This is used to relinquish the ability + to do certain operations which are considered to be + privileged on a usbfs file descriptor. + This includes claiming arbitrary interfaces, resetting + a device on which there are currently claimed interfaces + from other users, and issuing USBDEVFS_IOCTL calls. + The ioctl parameter is a 32 bit mask of interfaces + the user is allowed to claim on this file descriptor. + You may issue this ioctl more than one time to narrow + said mask. + -- cgit v1.2.3