[PATCH v2 3/3] scsi:libiscsi: teardown iscsi_cls_conn gracefully

[Wenchao Hao <haowenchao@huawei.com>]

commit 1b8d0300a3e9 ("scsi: libiscsi: Fix UAF in
iscsi_conn_get_param()/iscsi_conn_teardown()") fixed an UAF in
iscsi_conn_get_param() and introduced 2 tmp_xxx varibles, the
implement looks ugly.

We can fix this UAF with the help of device_del() gracefully.
Call iscsi_remove_conn() at the beginning of iscsi_conn_teardown would
make userspace unable to see iscsi_cls_conn any more, then we can free
memory safely.

Signed-off-by: Wenchao Hao <haowenchao@huawei.com>
Signed-off-by: Wu Bo <wubo40@huawei.com>
---
 drivers/scsi/libiscsi.c             | 8 ++++----
 drivers/scsi/scsi_transport_iscsi.c | 3 ++-
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 43f903bce0b8..0d57521751dd 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -3109,8 +3109,8 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn)
 {
 	struct iscsi_conn *conn = cls_conn->dd_data;
 	struct iscsi_session *session = conn->session;
-	char *tmp_persistent_address = conn->persistent_address;
-	char *tmp_local_ipaddr = conn->local_ipaddr;
+
+	iscsi_remove_conn(cls_conn);
 
 	del_timer_sync(&conn->transport_timer);
 
@@ -3132,6 +3132,8 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn)
 	spin_lock_bh(&session->frwd_lock);
 	free_pages((unsigned long) conn->data,
 		   get_order(ISCSI_DEF_MAX_RECV_SEG_LEN));
+	kfree(conn->persistent_address);
+	kfree(conn->local_ipaddr);
 	/* regular RX path uses back_lock */
 	spin_lock_bh(&session->back_lock);
 	kfifo_in(&session->cmdpool.queue, (void*)&conn->login_task,
@@ -3143,8 +3145,6 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn)
 	mutex_unlock(&session->eh_mutex);
 
 	iscsi_destroy_conn(cls_conn);
-	kfree(tmp_persistent_address);
-	kfree(tmp_local_ipaddr);
 }
 EXPORT_SYMBOL_GPL(iscsi_conn_teardown);
 
diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
index ca724eed4f4d..7b4d998708e7 100644
--- a/drivers/scsi/scsi_transport_iscsi.c
+++ b/drivers/scsi/scsi_transport_iscsi.c
@@ -2165,6 +2165,7 @@ static int iscsi_iter_destroy_conn_fn(struct device *dev, void *data)
 {
 	if (!iscsi_is_conn_dev(dev))
 		return 0;
+	iscsi_remove_conn(iscsi_dev_to_conn(dev));
 	return iscsi_destroy_conn(iscsi_dev_to_conn(dev));
 }
 
@@ -2463,7 +2464,7 @@ int iscsi_destroy_conn(struct iscsi_cls_conn *conn)
 
 	transport_unregister_device(&conn->dev);
 	ISCSI_DBG_TRANS_CONN(conn, "Completing conn destruction\n");
-	device_unregister(&conn->dev);
+	iscsi_free_conn(conn);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(iscsi_destroy_conn);
-- 
2.32.0