[PATCH] libiscsi: fix UAF when iscsi_conn_get_param and iscsi_conn_teardown concurrent

[lixiaokeng <lixiaokeng@huawei.com>]

|- iscsi_if_destroy_conn            |-dev_attr_show
 |-iscsi_conn_teardown
  |-spin_lock_bh                     |-iscsi_sw_tcp_conn_get_param

  |-kfree(conn->persistent_address)   |-iscsi_conn_get_param
  |-kfree(conn->local_ipaddr)
                                       ==>|-read persistent_address
                                       ==>|-read local_ipaddr
  |-spin_unlock_bh

when iscsi_conn_teardown and iscsi_conn_get_param happen in parallel,
may trigger UAF issues.

Signed-off-by: Lixiaokeng<lixiaokeng@huawei.com>
Signed-off-by: Linfeilong<linfeilong@huawei.com>
Reported-by: Lu Tixiong<lutianxiong@huawei.com>
---
 drivers/scsi/libiscsi.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 284b939fb1ea..059dae8909ee 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -3100,6 +3100,8 @@ 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;

 	del_timer_sync(&conn->transport_timer);

@@ -3121,8 +3123,6 @@ 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,
@@ -3134,6 +3134,8 @@ 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);

--