• Jason Gerecke's avatar
    HID: wacom: Always increment hdev refcount within wacom_get_hdev_data · 2a5e597c
    Jason Gerecke authored
    The wacom_get_hdev_data function is used to find and return a reference to
    the "other half" of a Wacom device (i.e., the touch device associated with
    a pen, or vice-versa). To ensure these references are properly accounted
    for, the function is supposed to automatically increment the refcount before
    returning. This was not done, however, for devices which have pen & touch
    on different interfaces of the same USB device. This can lead to a WARNING
    ("refcount_t: underflow; use-after-free") when removing the module or device
    as we call kref_put() more times than kref_get(). Triggering an "actual" use-
    after-free would be difficult since both devices will disappear nearly-
    simultaneously. To silence this warning and prevent the potential error, we
    need to increment the refcount for all cases within wacom_get_hdev_data.
    
    Fixes: 41372d5d ("HID: wacom: Augment 'oVid' and 'oPid' with heuristics for HID_GENERIC")
    Cc: <stable@vger.kernel.org> # v4.9+
    Signed-off-by: default avatarJason Gerecke <jason.gerecke@wacom.com>
    Reviewed-by: default avatarPing Cheng <ping.cheng@wacom.com>
    Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
    2a5e597c
wacom_sys.c 67.6 KB