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patch "kobject: Make sure the parent does not get released before its" added to driver-core-linus

PATCH [email protected] 1 participant 1 message May 21, 2020

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This is a note to let you know that I've just added the patch titled

kobject: Make sure the parent does not get released before its

to my driver-core git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git
in the driver-core-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 4ef12f7198023c09ad6d25b652bd8748c965c7fa Mon Sep 17 00:00:00 2001
From: Heikki Krogerus <[email protected]>
Date: Wed, 13 May 2020 18:18:40 +0300
Subject: kobject: Make sure the parent does not get released before its
children

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 <[email protected]>
Reported-by kernel test robot <[email protected]>
Fixes 7589238a8cf3 ("Revert "software node: Simplify software_node_release() function"")
Suggested-by "Rafael J. Wysocki" <[email protected]>
Signed-off-by Heikki Krogerus <[email protected]>
Reviewed-by Rafael J. Wysocki <[email protected]>
Reviewed-by Brendan Higgins <[email protected]>
Tested-by Brendan Higgins <[email protected]>
Acked-by Randy Dunlap <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Cc stable <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 lib/kobject.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)
lib/kobject.c +20 -10
index 83198cb37d8d..2bd631460e18 100644
@@ -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
Signature · 1 line
2.26.2