• Johan Hovold's avatar
    gpio: sysfs: fix memory leaks and device hotplug · 483d8211
    Johan Hovold authored
    Unregister GPIOs requested through sysfs at chip remove to avoid leaking
    the associated memory and sysfs entries.
    
    The stale sysfs entries prevented the gpio numbers from being exported
    when the gpio range was later reused (e.g. at device reconnect).
    
    This also fixes the related module-reference leak.
    
    Note that kernfs makes sure that any on-going sysfs operations finish
    before the class devices are unregistered and that further accesses
    fail.
    
    The chip exported flag is used to prevent gpiod exports during removal.
    This also makes it harder to trigger, but does not fix, the related race
    between gpiochip_remove and export_store, which is really a race with
    gpiod_request that needs to be addressed separately.
    
    Also note that this would prevent the crashes (e.g. NULL-dereferences)
    at reconnect that affects pre-3.18 kernels, as well as use-after-free on
    operations on open attribute files on pre-3.14 kernels (prior to
    kernfs).
    
    Fixes: d8f388d8 ("gpio: sysfs interface")
    Cc: stable <stable@vger.kernel.org>	# v2.6.27: 01cca93aSigned-off-by: default avatarJohan Hovold <johan@kernel.org>
    Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
    483d8211
gpiolib-sysfs.c 20 KB