On Tue, Jun 16, 2020 at 5:50 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
From: Heikki Krogerus heikki.krogerus@linux.intel.com
[ Upstream commit 4ef12f7198023c09ad6d25b652bd8748c965c7fa ]
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"") Suggested-by: "Rafael J. Wysocki" rafael@kernel.org Signed-off-by: Heikki Krogerus heikki.krogerus@linux.intel.com Reviewed-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Brendan Higgins brendanhiggins@google.com Tested-by: Brendan Higgins brendanhiggins@google.com Acked-by: Randy Dunlap rdunlap@infradead.org Link: https://lore.kernel.org/r/20200513151840.36400-1-heikki.krogerus@linux.intel... Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org
lib/kobject.c | 30 ++++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-)
diff --git a/lib/kobject.c b/lib/kobject.c index 83198cb37d8d..2bd631460e18 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);
This is known incorrect, because that should only be done if the __kobject_del() above has run.
Also this commit has been reverted from the mainline.
I have posted a fixed replacement for it with no response whatever so far:
https://lore.kernel.org/lkml/1908555.IiAGLGrh1Z@kreacher/
}
#ifdef CONFIG_DEBUG_KOBJECT_RELEASE