scsi: libiscsi: Fix UAF in iscsi_conn_get_param()/iscsi_conn_teardown()

|- 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, a
UAF may be triggered.

Link: https://lore.kernel.org/r/046ec8a0-ce95-d3fc-3235-666a7c65b224@huawei.com
Reported-by: Lu Tixiong <lutianxiong@huawei.com>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Lixiaokeng <lixiaokeng@huawei.com>
Signed-off-by: Linfeilong <linfeilong@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 284b939fb1eafbd8f443b1993bb941ab9029dfa0..059dae8909ee539350ad3abeca974237896b2cc5 100644 (file)
--- 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);