On Thu, 4 Feb 2016, Emilio López wrote:
> From: Reilly Grant <reillyg@xxxxxxxxxxxx>
>
> 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.
>
> Signed-off-by: Reilly Grant <reillyg@xxxxxxxxxxxx>
> Signed-off-by: Emilio López <emilio.lopez@xxxxxxxxxxxxxxx>
>
> ---
>
> Changes in v3:
> - Switch ioctl to use a __u32 given the iface qty is capped at 32
> - Reword comments as requested by Alan
> - Allow callers to shrink the allowed interfaces mask
> @@ -624,6 +626,10 @@ static int claimintf(struct usb_dev_state *ps, unsigned int ifnum)
> if (test_bit(ifnum, &ps->ifclaimed))
> return 0;
>
> + if (ps->privileges_dropped
> + && !test_bit(ifnum, &ps->interface_allowed_mask))
Continuation lines in this file are indented by 2 tab stops, not 1
space.
> @@ -1198,6 +1202,27 @@ static int proc_connectinfo(struct usb_dev_state *ps, void __user *arg)
>
> static int proc_resetdevice(struct usb_dev_state *ps)
> {
> + struct usb_host_config *actconfig = ps->dev->actconfig;
> + struct usb_interface *interface;
> + int i, number;
> +
> + /* Don't allow a device reset if the process has dropped the
> + * privilege to do such things and any of the interfaces are
> + * currently claimed.
> + */
> + if (ps->privileges_dropped && actconfig) {
> + for (i = 0; i < actconfig->desc.bNumInterfaces; ++i) {
> + interface = actconfig->interface[i];
> + number = interface->cur_altsetting->desc.bInterfaceNumber;
> + if (usb_interface_claimed(interface)) {
The test should be:
if (usb_interface_claimed(interface) &&
!test_bit(number, &ps->ifclaimed)) {
We don't want to prevent people from resetting a device merely because
they have claimed an interface. Only if someone else has claimed one.
> + dev_warn(&ps->dev->dev,
> + "usbfs: interface %d claimed by %s while '%s' resets device\n",
> + number, interface->dev.driver->name, current->comm);
> + return -EACCES;
> + }
> + }
> + }
> +
> return usb_reset_device(ps->dev);
> }
Also, it wouldn't hurt to change proc_get_capabilities() and
include/uapi/linux/usbdevicefs.h to add a USBDEVFS_CAP_DROP_PRIVILEGES
bit.
Alan Stern
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