[PATCH v2] kset: fix memory leak when kset_register() returns error

From: Yang Yingliang <yangyingliang@huawei.com>
To: <linux-kernel@vger.kernel.org>, <qemu-devel@nongnu.org>,
	<linux-f2fs-devel@lists.sourceforge.net>,
	<linux-erofs@lists.ozlabs.org>, <ocfs2-devel@oss.oracle.com>,
	<linux-mtd@lists.infradead.org>, <amd-gfx@lists.freedesktop.org>
Cc: <gregkh@linuxfoundation.org>, <rafael@kernel.org>,
	<somlo@cmu.edu>, <mst@redhat.com>, <jaegeuk@kernel.org>,
	<chao@kernel.org>, <hsiangkao@linux.alibaba.com>,
	<huangjianan@oppo.com>, <mark@fasheh.com>, <jlbec@evilplan.org>,
	<joseph.qi@linux.alibaba.com>, <akpm@linux-foundation.org>,
	<alexander.deucher@amd.com>, <luben.tuikov@amd.com>,
	<richard@nod.at>, <liushixin2@huawei.com>
Subject: [PATCH v2] kset: fix memory leak when kset_register() returns error
Date: Mon, 24 Oct 2022 20:19:10 +0800	[thread overview]
Message-ID: <20221024121910.1169801-1-yangyingliang@huawei.com> (raw)

Inject fault while loading module, kset_register() may fail.
If it fails, the name allocated by kobject_set_name() which
is called before kset_register() is leaked, because refcount
of kobject is hold in kset_init().

As a kset may be embedded in a larger structure which needs
be freed in release() function or error path in callers, we
can not call kset_put() in kset_register(), or it will cause
double free, so just call kfree_const() to free the name and
set it to NULL.

With this fix, the callers don't need to care about the name
freeing and call an extra kset_put() if kset_register() fails.

Suggested-by: Luben Tuikov <luben.tuikov@amd.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
v1 -> v2:
  Free name inside of kset_register() instead of calling kset_put()
  in drivers.
---
 lib/kobject.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/kobject.c b/lib/kobject.c
index a0b2dbfcfa23..3409a89c81e5 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -834,6 +834,9 @@ EXPORT_SYMBOL_GPL(kobj_sysfs_ops);
 /**
  * kset_register() - Initialize and add a kset.
  * @k: kset.
+ *
+ * NOTE: On error, the kset.kobj.name allocated by() kobj_set_name()
+ * which is called before kset_register() in caller need be freed.
  */
 int kset_register(struct kset *k)
 {
@@ -844,8 +847,11 @@ int kset_register(struct kset *k)
 
 	kset_init(k);
 	err = kobject_add_internal(&k->kobj);
-	if (err)
+	if (err) {
+		kfree_const(k->kobj.name);
+		k->kobj.name = NULL;
 		return err;
+	}
 	kobject_uevent(&k->kobj, KOBJ_ADD);
 	return 0;
 }
-- 
2.25.1


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