From: Ingo Rohloff ingo.rohloff@lauterbach.com
[ Upstream commit abb0b3d96a1f9407dd66831ae33985a386d4200d ]
commit 1455cf8dbfd0 ("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 --- drivers/usb/core/devio.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c index 62b2a7105f023..4fb4cf8c2f14d 100644 --- a/drivers/usb/core/devio.c +++ b/drivers/usb/core/devio.c @@ -755,8 +755,15 @@ static int claimintf(struct usb_dev_state *ps, unsigned int ifnum) intf = usb_ifnum_to_if(dev, ifnum); if (!intf) err = -ENOENT; - else + else { + unsigned int old_suppress; + + /* suppress uevents while claiming interface */ + old_suppress = dev_get_uevent_suppress(&intf->dev); + dev_set_uevent_suppress(&intf->dev, 1); err = usb_driver_claim_interface(&usbfs_driver, intf, ps); + dev_set_uevent_suppress(&intf->dev, old_suppress); + } if (err == 0) set_bit(ifnum, &ps->ifclaimed); return err; @@ -776,7 +783,13 @@ static int releaseintf(struct usb_dev_state *ps, unsigned int ifnum) if (!intf) err = -ENOENT; else if (test_and_clear_bit(ifnum, &ps->ifclaimed)) { + unsigned int old_suppress; + + /* suppress uevents while releasing interface */ + old_suppress = dev_get_uevent_suppress(&intf->dev); + dev_set_uevent_suppress(&intf->dev, 1); usb_driver_release_interface(&usbfs_driver, intf); + dev_set_uevent_suppress(&intf->dev, old_suppress); err = 0; } return err;