The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3d1cf435e201d1fd63e4346b141881aed086effd Mon Sep 17 00:00:00 2001

From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com Date: Fri, 15 Jan 2021 19:30:51 +0100 Subject: [PATCH] driver core: Extend device_is_dependent()

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

diff --git a/drivers/base/core.c b/drivers/base/core.c index 25e08e5f40bd..3819fd012e27 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -208,6 +208,16 @@ int device_links_read_lock_held(void) #endif #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. @@ -221,7 +231,12 @@ 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);