On Mon, Mar 1, 2021 at 10:05 AM Johan Hovold [off-list ref] wrote:

Fix a NULL-pointer deference when deregistering the gpio character
device that was introduced by the recent stub-driver hack. When the new
"driver" is unbound as part of deregistration, driver core clears the
driver-data pointer which is used to retrieve the struct gpio_device in
its release callback.

Fix this by using container_of() in the release callback as should have
been done all along.

Fixes: 4731210c09f5 ("gpiolib: Bind gpio_device to a driver to enable fw_devlink=on by default")
Cc: Saravana Kannan <redacted>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reported-by: syzbot+d27b4c8adbbff70fbfde@syzkaller.appspotmail.com
Signed-off-by: Johan Hovold <johan@kernel.org>

Oh nice catch!
Reviewed-by: Linus Walleij <redacted>

Yours,
Linus Walleij