ludovic coues schreef op 2015-08-10 23:29:
2015-08-10 22:56 GMT+02:00 Martin Pieuchot <m...@openbsd.org>:
On 30/07/15(Thu) 12:18, Ludovic Coues wrote:
Right now, an USB_REQUEST ioctl will fail with an EBADF error if done
on a device opened as read-only. With this patch, the ioctl will fail
only if the USB_REQUEST is a write request.
Do you need this to be able to use your usbdevs-like tool as a normal
use with the "w" bit on a /dev/usb node?
In the case a user have the read right on the node without the write
right, this patch would allow the normal use of my usbdevs-like tools
for this user.
In a system with default permission, this won't change anything as
root and wheel have read + write permission on /dev/usb nodes and
everybody else have nothing.
Well, the point is that the USB_REQUEST ioctl sends a command to the
device.
In that sense, it always involves a "write" to the device even if the
command
issued is a "read" command. The fact that there is only data transfer
from the
device to the host doesn't mean it doesn't affect the state of the
device.
I think the current code is right. If you open the node read-only, you
only
get to see the kernel state for the device. If you open with write
permission,
you get full control over the device.
