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However, if kobject_init_and_add() fails before acquiring the parent reference or drops it on error in kobject_add_internal(), swnode->kobj holds no reference on parent->kobj while swnode->parent remains set. With CONFIG_DEBUG_KOBJECT_RELEASE enabled, the random delay in kobject_delayed_cleanup() may create a situation where - when unregistering the child node and then the parent - the parent object gets released before the child who's left with a dangling pointer. Acquire a refernce to the parent swnode when registering the child and drop it on child's release. Cc: stable@vger.kernel.org Fixes: 59abd83672f7 ("drivers: base: Introducing software nodes to the firmware node framework") Closes: https://sashiko.dev/#/bug/linux-82933c14-d212-49f1-bd2f-d4ab1e16fed7 Signed-off-by: Bartosz Golaszewski --- drivers/base/swnode.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c index 84a77ffa3dc4bbcca62bbe67c3390693500b01ea..986dcb933d2c9274e9000968f115d7fccc2d103f 100644 --- a/drivers/base/swnode.c +++ b/drivers/base/swnode.c @@ -843,11 +843,12 @@ static void software_node_free(const struct software_node *node) static void software_node_release(struct kobject *kobj) { struct swnode *swnode = kobj_to_swnode(kobj); + struct swnode *parent = swnode->parent; fwnode_links_purge(&swnode->fwnode); - if (swnode->parent) { - ida_free(&swnode->parent->child_ids, swnode->id); + if (parent) { + ida_free(&parent->child_ids, swnode->id); list_del(&swnode->entry); } else { ida_free(&swnode_root_ids, swnode->id); @@ -858,6 +859,9 @@ static void software_node_release(struct kobject *kobj) ida_destroy(&swnode->child_ids); kfree(swnode); + + if (parent) + swnode_put(parent); } static const struct kobj_type software_node_type = { @@ -885,7 +889,7 @@ swnode_register(const struct software_node *node, struct swnode *parent, swnode->id = ret; swnode->node = node; - swnode->parent = parent; + swnode->parent = parent ? swnode_get(parent) : NULL; swnode->kobj.kset = swnode_kset; fwnode_init(&swnode->fwnode, &software_node_ops); --- base-commit: ddfe51b0a0f5dc9e415cc2c8ad8db17532dd426b change-id: 20261106-swnode-kobject-parent-ref-3bd9b9b75aeb Best regards, -- Bartosz Golaszewski