From: Heikki Krogerus heikki.krogerus@linux.intel.com
[ Upstream commit 079ad2fb4bf9eba8a0aaab014b49705cd7f07c66 ]
If kobject_del() is invoked by kobject_cleanup() to delete the target kobject, it may cause its parent kobject to be freed before invoking the target kobject's ->release() method, which effectively means freeing the parent before dealing with the child entirely.
That is confusing at best and it may also lead to functional issues if the callers of kobject_cleanup() are not careful enough about the order in which these calls are made, so avoid the problem by making kobject_cleanup() drop the last reference to the target kobject's parent at the end, after invoking the target kobject's ->release() method.
[ rjw: Rewrite the subject and changelog, make kobject_cleanup() drop the parent reference only when __kobject_del() has been called. ]
Reported-by: Naresh Kamboju naresh.kamboju@linaro.org Reported-by: kernel test robot rong.a.chen@intel.com Fixes: 7589238a8cf3 ("Revert "software node: Simplify software_node_release() function"") Suggested-by: Rafael J. Wysocki rafael@kernel.org Signed-off-by: Heikki Krogerus heikki.krogerus@linux.intel.com Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Link: https://lore.kernel.org/r/1908555.IiAGLGrh1Z@kreacher Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- lib/kobject.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-)
diff --git a/lib/kobject.c b/lib/kobject.c index 1e4b7382a88ed..3afb939f2a1cc 100644 --- a/lib/kobject.c +++ b/lib/kobject.c @@ -599,14 +599,7 @@ int kobject_move(struct kobject *kobj, struct kobject *new_parent) } EXPORT_SYMBOL_GPL(kobject_move);
-/** - * kobject_del() - Unlink kobject from hierarchy. - * @kobj: object. - * - * This is the function that should be called to delete an object - * successfully added via kobject_add(). - */ -void kobject_del(struct kobject *kobj) +static void __kobject_del(struct kobject *kobj) { struct kernfs_node *sd; const struct kobj_type *ktype; @@ -632,9 +625,23 @@ void kobject_del(struct kobject *kobj)
kobj->state_in_sysfs = 0; kobj_kset_leave(kobj); - kobject_put(kobj->parent); kobj->parent = NULL; } + +/** + * kobject_del() - Unlink kobject from hierarchy. + * @kobj: object. + * + * This is the function that should be called to delete an object + * successfully added via kobject_add(). + */ +void kobject_del(struct kobject *kobj) +{ + struct kobject *parent = kobj->parent; + + __kobject_del(kobj); + kobject_put(parent); +} EXPORT_SYMBOL(kobject_del);
/** @@ -670,6 +677,7 @@ EXPORT_SYMBOL(kobject_get_unless_zero); */ static void kobject_cleanup(struct kobject *kobj) { + struct kobject *parent = kobj->parent; struct kobj_type *t = get_ktype(kobj); const char *name = kobj->name;
@@ -684,7 +692,10 @@ static void kobject_cleanup(struct kobject *kobj) if (kobj->state_in_sysfs) { pr_debug("kobject: '%s' (%p): auto cleanup kobject_del\n", kobject_name(kobj), kobj); - kobject_del(kobj); + __kobject_del(kobj); + } else { + /* avoid dropping the parent reference unnecessarily */ + parent = NULL; }
if (t && t->release) { @@ -698,6 +709,8 @@ static void kobject_cleanup(struct kobject *kobj) pr_debug("kobject: '%s': free name\n", name); kfree_const(name); } + + kobject_put(parent); }
#ifdef CONFIG_DEBUG_KOBJECT_RELEASE