Only the overlay notifier callbacks have a chance to potentially get hold of references to those two resources, but they are not supposed to store them beyond OF_OVERLAY_POST_REMOVE.
Document the overlay notifier API, its constraint regarding pointer lifetime, and then remove intentional leaks of ovcs->overlay_tree and ovcs->fdt from free_overlay_changeset. See also https://lkml.org/lkml/2018/4/23/1063 and following. Signed-off-by: Jan Kiszka <jan.kis...@siemens.com> --- Documentation/devicetree/overlay-notes.txt | 8 ++++++++ drivers/of/overlay.c | 30 +++++++++++++++++++++--------- 2 files changed, 29 insertions(+), 9 deletions(-) diff --git a/Documentation/devicetree/overlay-notes.txt b/Documentation/devicetree/overlay-notes.txt index a4feb6dde8cd..725fb8d255c1 100644 --- a/Documentation/devicetree/overlay-notes.txt +++ b/Documentation/devicetree/overlay-notes.txt @@ -98,6 +98,14 @@ Finally, if you need to remove all overlays in one-go, just call of_overlay_remove_all() which will remove every single one in the correct order. +In addition, there is the option to register notifiers that get called on +overlay operations. See of_overlay_notifier_register/unregister and +enum of_overlay_notify_action for details. + +Note that a notifier callback is not supposed to store pointers to a device +tree node or its content beyond OF_OVERLAY_POST_REMOVE corresponding to the +respective node it received. + Overlay DTS Format ------------------ diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c index b35fe88f1851..7baa53e5b1d7 100644 --- a/drivers/of/overlay.c +++ b/drivers/of/overlay.c @@ -102,12 +102,28 @@ static DEFINE_IDR(ovcs_idr); static BLOCKING_NOTIFIER_HEAD(overlay_notify_chain); +/** + * of_overlay_notifier_register() - Register notifier for overlay operations + * @nb: Notifier block to register + * + * Register for notification on overlay operations on device tree nodes. The + * reported actions definied by @of_reconfig_change. The notifier callback + * furthermore receives a pointer to the affected device tree node. + * + * Note that a notifier callback is not supposed to store pointers to a device + * tree node or its content beyond @OF_OVERLAY_POST_REMOVE corresponding to the + * respective node it received. + */ int of_overlay_notifier_register(struct notifier_block *nb) { return blocking_notifier_chain_register(&overlay_notify_chain, nb); } EXPORT_SYMBOL_GPL(of_overlay_notifier_register); +/** + * of_overlay_notifier_register() - Unregister notifier for overlay operations + * @nb: Notifier block to unregister + */ int of_overlay_notifier_unregister(struct notifier_block *nb) { return blocking_notifier_chain_unregister(&overlay_notify_chain, nb); @@ -671,17 +687,13 @@ static void free_overlay_changeset(struct overlay_changeset *ovcs) of_node_put(ovcs->fragments[i].overlay); } kfree(ovcs->fragments); - /* - * TODO - * - * would like to: kfree(ovcs->overlay_tree); - * but can not since drivers may have pointers into this data - * - * would like to: kfree(ovcs->fdt); - * but can not since drivers may have pointers into this data + * There should be no live pointers into ovcs->overlay_tree and + * ovcs->fdt due to the policy that overlay notifiers are not allowed + * to retain pointers into the overlay devicetree. */ - + kfree(ovcs->overlay_tree); + kfree(ovcs->fdt); kfree(ovcs); } -- 2.13.6
