Re: [PATCH] Input: pxrc - fix leak of usb_device

On Sun, Jul 15, 2018 at 10:42 AM Marcus Folkesson
[off-list ref] wrote:

On Sat, Jul 14, 2018 at 08:51:09AM +0000, Dmitry Torokhov wrote:

quoted

On Sat, Jul 14, 2018 at 10:09:20AM +0200, Marcus Folkesson wrote:

quoted

Hi Alexey,

Good catch!

On Fri, Jul 13, 2018 at 11:07:57PM +0300, Alexey Khoroshilov wrote:

quoted

pxrc_probe() calls usb_get_dev(), but there is no usb_put_dev()
anywhere in the driver.

The patch adds one to error handling code and to pxrc_disconnect().

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <redacted>

Reviewed-by: Marcus Folkesson <marcus.folkesson@gmail.com>

Hmm, the biggest question however if we need to "take" the device, as I
do not think interface can outlive the device, and whether we actually
need to store it in pxrc, as we only need it during set up, as far as I
can see.

Yep, the device is only used during setup.
I interpret the comments for usb_get_dev() as you should take a
reference count on the device even if you only use the interface, but I
could be wrong.

From usb_get_dev()::

         * usb_get_dev - increments the reference count of the usb device structure
         * @dev: the device being referenced
         *
         * Each live reference to a device should be refcounted.
         *
         * Drivers for USB interfaces should normally record such references in
         * their probe() methods, when they bind to an interface, and release
         * them by calling usb_put_dev(), in their disconnect() methods.

Hmm, usb device is a parent of usb interface so our driver model rules
ensure that usb device should not disappear while interface device is
still there. Greg, is this comment still valid?

I can fix the driver to not take the device if that is what we want.
If not Alexey want to fix it of course, it is his catch :-)

Yeah, I'd prefer doing this if possible.

Thanks.

-- 
Dmitry