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From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org,
	Naresh Kamboju <naresh.kamboju@linaro.org>,
	kernel test robot <rong.a.chen@intel.com>,
	Brendan Higgins <brendanhiggins@google.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>
Subject: [PATCH] kobject: Make sure the parent does not get released before its children
Date: Wed, 13 May 2020 18:18:40 +0300
Message-ID: <20200513151840.36400-1-heikki.krogerus@linux.intel.com> (raw)

In the function kobject_cleanup(), kobject_del(kobj) is
called before the kobj->release(). That makes it possible to
release the parent of the kobject before the kobject itself.

To fix that, adding function __kboject_del() that does
everything that kobject_del() does except release the parent
reference. kobject_cleanup() then calls __kobject_del()
instead of kobject_del(), and separately decrements the
reference count of the parent kobject after kobj->release()
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"")
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Suggested-by: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
---
 lib/kobject.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/lib/kobject.c b/lib/kobject.c
index 65fa7bf70c57..32432036bef8 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;
@@ -625,9 +618,23 @@ 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);
 
 /**
@@ -663,6 +670,7 @@ 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 +692,7 @@ 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);
 	}
 
 	if (t && t->release) {
@@ -698,6 +706,8 @@ 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
-- 
2.26.2


             reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-13 15:18 Heikki Krogerus [this message]
2020-05-13 15:20 ` Rafael J. Wysocki
2020-05-13 15:42 ` Greg Kroah-Hartman
2020-05-13 15:51   ` Rafael J. Wysocki
2020-05-13 20:18 ` Brendan Higgins
2020-05-13 20:54   ` Randy Dunlap
2020-05-13 21:30 ` Brendan Higgins
2020-05-13 23:14   ` Randy Dunlap
2020-05-14  6:54     ` Heikki Krogerus
2020-05-15 15:10       ` Greg Kroah-Hartman
2020-05-23 13:21 ` Guenter Roeck
2020-05-23 13:29   ` Guenter Roeck
2020-05-23 14:04   ` Greg Kroah-Hartman
2020-05-23 15:36 ` Greg Kroah-Hartman
2020-05-23 15:44   ` Randy Dunlap
2020-05-23 19:04     ` Dmitry Torokhov
2020-05-24 11:42       ` Greg Kroah-Hartman
2020-05-24 12:57     ` Greg Kroah-Hartman
2020-05-24 13:14       ` Greg Kroah-Hartman
2020-05-24 13:28         ` Greg Kroah-Hartman
2020-05-24 15:35           ` Greg Kroah-Hartman

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