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From:   Yu Kuai <yukuai3@huawei.com>
To:     <hch@lst.de>, <axboe@kernel.dk>, <gregkh@linuxfoundation.org>,
        <willy@infradead.org>, <martin.petersen@oracle.com>,
        <kch@nvidia.com>
CC:     <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <yukuai3@huawei.com>, <yukuai1@huaweicloud.com>,
        <yi.zhang@huawei.com>
Subject: [PATCH RFC 1/2] kobject: add return value for kobject_put()
Date:   Tue, 18 Oct 2022 21:14:31 +0800
Message-ID: <20221018131432.434167-2-yukuai3@huawei.com>
In-Reply-To: <20221018131432.434167-1-yukuai3@huawei.com>
References: <20221018131432.434167-1-yukuai3@huawei.com>
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The return value will be used in later patch to fix uaf for slave_dir
and bd_holder_dir in block layer.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 include/linux/kobject.h | 2 +-
 lib/kobject.c           | 7 +++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/linux/kobject.h b/include/linux/kobject.h
index 57fb972fea05..f12de6274c51 100644
--- a/include/linux/kobject.h
+++ b/include/linux/kobject.h
@@ -110,7 +110,7 @@ extern int __must_check kobject_move(struct kobject *, struct kobject *);
 extern struct kobject *kobject_get(struct kobject *kobj);
 extern struct kobject * __must_check kobject_get_unless_zero(
 						struct kobject *kobj);
-extern void kobject_put(struct kobject *kobj);
+extern bool kobject_put(struct kobject *kobj);
 
 extern const void *kobject_namespace(struct kobject *kobj);
 extern void kobject_get_ownership(struct kobject *kobj,
diff --git a/lib/kobject.c b/lib/kobject.c
index a0b2dbfcfa23..f86c55ae7376 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -711,15 +711,18 @@ static void kobject_release(struct kref *kref)
  *
  * Decrement the refcount, and if 0, call kobject_cleanup().
  */
-void kobject_put(struct kobject *kobj)
+bool kobject_put(struct kobject *kobj)
 {
 	if (kobj) {
 		if (!kobj->state_initialized)
 			WARN(1, KERN_WARNING
 				"kobject: '%s' (%p): is not initialized, yet kobject_put() is being called.\n",
 			     kobject_name(kobj), kobj);
-		kref_put(&kobj->kref, kobject_release);
+		if (kref_put(&kobj->kref, kobject_release))
+			return true;
 	}
+
+	return false;
 }
 EXPORT_SYMBOL(kobject_put);
 
-- 
2.31.1