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[ Upstream commitabb0b3d96a] commit1455cf8dbf("driver core: emit uevents when device is bound to a driver") added bind and unbind uevents when a driver is bound or unbound to a physical device. For USB devices which are handled via the generic usbfs layer (via libusb for example), this is problematic: Each time a user space program calls ioctl(usb_fd, USBDEVFS_CLAIMINTERFACE, &usb_intf_nr); and then later ioctl(usb_fd, USBDEVFS_RELEASEINTERFACE, &usb_intf_nr); The kernel will now produce a bind or unbind event, which does not really contain any useful information. This allows a user space program to run a DoS attack against programs which listen to uevents (in particular systemd/eudev/upowerd): A malicious user space program just has to call in a tight loop ioctl(usb_fd, USBDEVFS_CLAIMINTERFACE, &usb_intf_nr); ioctl(usb_fd, USBDEVFS_RELEASEINTERFACE, &usb_intf_nr); With this loop the malicious user space program floods the kernel and all programs listening to uevents with tons of bind and unbind events. This patch suppresses uevents for ioctls USBDEVFS_CLAIMINTERFACE and USBDEVFS_RELEASEINTERFACE. Signed-off-by: Ingo Rohloff <ingo.rohloff@lauterbach.com> Link: https://lore.kernel.org/r/20191011115518.2801-1-ingo.rohloff@lauterbach.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("hub_wq").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.