From f4cdf7ca9a1fdcca413157df19753f388a5a224e Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 19 Aug 2026 10:09:22 -0700 Subject: Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media Pull media updates from Mauro Carvalho Chehab: - v4l2-core: added ISP statistics support and per-block validation - v4l2-core: Allow unknown HDR10 white point and luminance - New camera sensors: Sony IMX678 and IMX471m, Himax HM1092 IR sensor - New codec: Milos: VPU v2.0 codec support - isp driver: gained support for Dreamchip RPPX1 ISP framework - vsp1 driver: gained support for RZ/T2H and RZ/N2H - Novalake driver: gained CVS support for new NVL hardware - dvb-core: fix feed leak on failed DMX_ADD_PID - several driver fixes, cleanups and minor improvements * tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (308 commits) media: ipu-bridge: check all DMI entries when overriding sensor rotation media: v4l2-async: avoid deleting unlinked ASC entry on link error media: rzg2l-cru: Align bytesperline to hardware DMA stride requirement media: intel/ipu6: fix async notifier cleanup leak on parse error media: staging/ipu7: fix async notifier UAF on probe error path media: amd: isp4: fix self-deadlock in isp4sd_pwron_and_init() error path media: amd: isp4: release partial allocations in isp4if_alloc_fw_gpumem() media: rcar-isp: Fix VSPX reference leaks media: rcar-isp: Release ISPCORE resources media: i2c: imx415: Release runtime PM reference on VBLANK error media: i2c: imx415: Return test pattern write errors media: renesas: vsp1: Declare index variables in for loop statement media: renesas: vsp1: Make reset control optional to support platforms without a reset line media: dt-bindings: media: renesas,vsp1: Document RZ/T2H and RZ/N2H SoCs media: dt-bindings: media: renesas,fcp: Document RZ/T2H and RZ/N2H SoCs media: nxp: imx8-isi: Add additional 32-bit RGB format support media: nxp: imx8-isi: Add 16-bit raw Bayer format support media: nxp: imx8-isi: Implement per-stream reference counting for multiplexed streams media: nxp: imx8-isi: Use BIT_ULL() for 64-bit stream masks media: nxp: imx8-isi: Correct color map between V4L2 and ISI ... --- Documentation/usb/authorization.rst | 129 ++++++++++++++++++++++++++++++++++++ 1 file changed, 129 insertions(+) create mode 100644 Documentation/usb/authorization.rst (limited to 'Documentation/usb/authorization.rst') diff --git a/Documentation/usb/authorization.rst b/Documentation/usb/authorization.rst new file mode 100644 index 000000000..150a14970 --- /dev/null +++ b/Documentation/usb/authorization.rst @@ -0,0 +1,129 @@ +============================================================== +Authorizing (or not) your USB devices to connect to the system +============================================================== + +Copyright (C) 2007 Inaky Perez-Gonzalez Intel Corporation + +This feature allows you to control if a USB device can be used (or +not) in a system. This feature will allow you to implement a lock-down +of USB devices, fully controlled by user space. + +As of now, when a USB device is connected it is configured and +its interfaces are immediately made available to the users. With this +modification, only if root authorizes the device to be configured will +then it be possible to use it. + +Usage +===== + +Authorize a device to connect:: + + $ echo 1 > /sys/bus/usb/devices/DEVICE/authorized + +De-authorize a device:: + + $ echo 0 > /sys/bus/usb/devices/DEVICE/authorized + +Set new devices connected to hostX to be deauthorized by default (ie: +lock down):: + + $ echo 0 > /sys/bus/usb/devices/usbX/authorized_default + +Remove the lock down:: + + $ echo 1 > /sys/bus/usb/devices/usbX/authorized_default + +By default, all USB devices are authorized. Writing "2" to the +authorized_default attribute causes the kernel to authorize by default +only devices connected to internal USB ports. + + +Example system lockdown (lame) +------------------------------ + +Imagine you want to implement a lockdown so only devices of type XYZ +can be connected (for example, it is a kiosk machine with a visible +USB port):: + + boot up + rc.local -> + + for host in /sys/bus/usb/devices/usb* + do + echo 0 > $host/authorized_default + done + +Hookup an script to udev, for new USB devices:: + + if device_is_my_type $DEV + then + echo 1 > $device_path/authorized + done + + +Now, device_is_my_type() is where the juice for a lockdown is. Just +checking if the class, type and protocol match something is the worse +security verification you can make (or the best, for someone willing +to break it). If you need something secure, use crypto and Certificate +Authentication or stuff like that. Something simple for an storage key +could be:: + + function device_is_my_type() + { + echo 1 > authorized # temporarily authorize it + # FIXME: make sure none can mount it + mount DEVICENODE /mntpoint + sum=$(md5sum /mntpoint/.signature) + if [ $sum = $(cat /etc/lockdown/keysum) ] + then + echo "We are good, connected" + umount /mntpoint + # Other stuff so others can use it + else + echo 0 > authorized + fi + } + + +Of course, this is lame, you'd want to do a real certificate +verification stuff with PKI, so you don't depend on a shared secret, +etc, but you get the idea. Anybody with access to a device gadget kit +can fake descriptors and device info. Don't trust that. You are +welcome. + + +Interface authorization +----------------------- + +There is a similar approach to allow or deny specific USB interfaces. +That allows to block only a subset of an USB device. + +Authorize an interface:: + + $ echo 1 > /sys/bus/usb/devices/INTERFACE/authorized + +Deauthorize an interface:: + + $ echo 0 > /sys/bus/usb/devices/INTERFACE/authorized + +The default value for new interfaces +on a particular USB bus can be changed, too. + +Allow interfaces per default:: + + $ echo 1 > /sys/bus/usb/devices/usbX/interface_authorized_default + +Deny interfaces per default:: + + $ echo 0 > /sys/bus/usb/devices/usbX/interface_authorized_default + +Per default the interface_authorized_default bit is 1. +So all interfaces would authorized per default. + +Note: + If a deauthorized interface will be authorized so the driver probing must + be triggered manually by writing INTERFACE to /sys/bus/usb/drivers_probe + +For drivers that need multiple interfaces all needed interfaces should be +authorized first. After that the drivers should be probed. +This avoids side effects. -- cgit v1.3.1