On Fri, Dec 08, 2023 at 12:31:24PM -0800, Douglas Anderson wrote:
> It's possible that usb_choose_configuration() can get called when a
> USB device has no driver. In this case the recent commit a87b8e3be926
> ("usb: core: Allow subclassed USB drivers to override
> usb_choose_configuration()") can cause a crash since it dereferenced
> the driver structure without checking for NULL. Let's add a check.
>
> This was seen in the real world when usbguard got ahold of a r8152
> device at the wrong time. It can also be simulated via this on a
> computer with one r8152-based USB Ethernet adapter:
> cd /sys/bus/usb/drivers/r8152-cfgselector
> to_unbind="$(ls -d *-*)"
> real_dir="$(readlink -f "${to_unbind}")"
> echo "${to_unbind}" > unbind
> cd "${real_dir}"
> echo 0 > authorized
> echo 1 > authorized
>
> Fixes: a87b8e3be926 ("usb: core: Allow subclassed USB drivers to override usb_choose_configuration()")
> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> ---
I'm not sure this is the best solution. A USB device with no driver is
an anomaly; in all likelihood we shouldn't be calling
usb_choose_configuration() for such a device in the first place.
So I think a better solution would be to put this check in
usb_authorize_device() before it does the autoresume, or else to make
usb_choose_configuration() return immediately, right at the start, if
there is no driver.
Alan Stern
