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SubjectRe: [PATCH v4] usb: devio: Add ioctl to disallow detaching kernel USB drivers.
On Sun, 14 Feb 2016, Emilio López wrote:

> From: Reilly Grant <reillyg@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.
>
> 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>
> Signed-off-by: Emilio López <emilio.lopez@collabora.co.uk>

Acked-by: Alan Stern <stern@rowland.harvard.edu>

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