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Date: Thu, 18 Feb 2016 13:44:46 -0500 (EST) From: Alan Stern <stern@...land.harvard.edu> To: Emilio López <emilio.lopez@...labora.co.uk> cc: gregkh@...uxfoundation.org, <kborer@...il.com>, <reillyg@...omium.org>, <keescook@...omium.org>, <linux-api@...r.kernel.org>, <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <jorgelo@...omium.org>, <dan.carpenter@...cle.com> Subject: Re: [PATCH v4] usb: devio: Add ioctl to disallow detaching kernel USB drivers. On Sun, 14 Feb 2016, Emilio López wrote: > From: Reilly Grant <reillyg@...omium.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. > > 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@...omium.org> > Signed-off-by: Emilio López <emilio.lopez@...labora.co.uk> Acked-by: Alan Stern <stern@...land.harvard.edu>
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