[ Upstream commit abb0b3d96a ]
commit 1455cf8dbf ("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>
cba6467277