From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> stable inclusion from linux-4.19.171 commit cfd402c22ca216e6be8d7337da427bfcfaa4e2b3 -------------------------------- commit 3d1cf435e201d1fd63e4346b141881aed086effd upstream. If the device passed as the target (second argument) to device_is_dependent() is not completely registered (that is, it has been initialized, but not added yet), but the parent pointer of it is set, it may be missing from the list of the parent's children and device_for_each_child() called by device_is_dependent() cannot be relied on to catch that dependency. For this reason, modify device_is_dependent() to check the ancestors of the target device by following its parent pointer in addition to the device_for_each_child() walk. Fixes: 9ed9895370ae ("driver core: Functional dependencies tracking support") Reported-by: Stephan Gerhold <stephan@gerhold.net> Tested-by: Stephan Gerhold <stephan@gerhold.net> Reviewed-by: Saravana Kannan <saravanak@google.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Link: https://lore.kernel.org/r/17705994.d592GUb2YH@kreacher Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> Signed-off-by: Cheng Jian <cj.chengjian@huawei.com> --- drivers/base/core.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index f0cdf38ed31c..e196e6a67e63 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -93,6 +93,16 @@ void device_links_read_unlock(int not_used) } #endif /* !CONFIG_SRCU */ +static bool device_is_ancestor(struct device *dev, struct device *target) +{ + while (target->parent) { + target = target->parent; + if (dev == target) + return true; + } + return false; +} + /** * device_is_dependent - Check if one device depends on another one * @dev: Device to check dependencies for. @@ -106,7 +116,12 @@ static int device_is_dependent(struct device *dev, void *target) struct device_link *link; int ret; - if (dev == target) + /* + * The "ancestors" check is needed to catch the case when the target + * device has not been completely initialized yet and it is still + * missing from the list of children of its parent device. + */ + if (dev == target || device_is_ancestor(dev, target)) return 1; ret = device_for_each_child(dev, target, device_is_dependent); -- 2.25.1