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

Revert "kobject: Make sure the parent does not get released before

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 e6764aa0e5530066dd969eccea2a1a7d177859a8 Mon Sep 17 00:00:00 2001

From: Greg Kroah-Hartman gregkh@linuxfoundation.org Date: Sat, 23 May 2020 17:11:11 +0200 Subject: Revert "kobject: Make sure the parent does not get released before its children"

This reverts commit 4ef12f7198023c09ad6d25b652bd8748c965c7fa.

Guenter reports:

All my arm64be (arm64 big endian) boot tests crash with this patch applied. Reverting it fixes the problem. Crash log and bisect results (from pending-fixes branch) below.

And also: arm64 images don't crash but report lots of "poison overwritten" backtraces like the one below. On arm, I see "refcount_t: underflow", also attached. I didn't bisect those, but given the context I would suspect the same culprit.

Reported-by: Guenter Roeck linux@roeck-us.net Link: https://lore.kernel.org/r/20200513151840.36400-1-heikki.krogerus@linux.intel... Cc: Naresh Kamboju naresh.kamboju@linaro.org Cc: kernel test robot rong.a.chen@intel.com Cc: "Rafael J. Wysocki" rafael@kernel.org Cc: Heikki Krogerus heikki.krogerus@linux.intel.com Cc: Brendan Higgins brendanhiggins@google.com Cc: Randy Dunlap rdunlap@infradead.org Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- lib/kobject.c | 30 ++++++++++-------------------- 1 file changed, 10 insertions(+), 20 deletions(-)

diff --git a/lib/kobject.c b/lib/kobject.c index 2bd631460e18..83198cb37d8d 100644 --- a/lib/kobject.c +++ b/lib/kobject.c @@ -599,7 +599,14 @@ int kobject_move(struct kobject *kobj, struct kobject *new_parent) } EXPORT_SYMBOL_GPL(kobject_move);

-static void __kobject_del(struct kobject *kobj) +/** + * 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 kernfs_node *sd; const struct kobj_type *ktype; @@ -618,23 +625,9 @@ static 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);

/** @@ -670,7 +663,6 @@ 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;

@@ -692,7 +684,7 @@ 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) { @@ -706,8 +698,6 @@ 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