From: Wenchao Hao <haowenchao@huawei.com>
Date: Wed, 9 Mar 2022 20:57:59 -0500
Subject: scsi: libiscsi: Teardown iscsi_cls_conn gracefully
Git-commit: 8709c323091be019f76a49cf783052a5636aca85
Patch-mainline: v5.18-rc1
References: bsc#1198410

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.

We can gracefully fix this UAF with the help of device_del(). Calling
iscsi_remove_conn() at the beginning of iscsi_conn_teardown would make
userspace unable to see iscsi_cls_conn. This way we we can free memory
safely.

Remove iscsi_destroy_conn() since it is no longer used.

[lduncan: needed for commit c577ab7ba5f3bf9062db8a58b6e89d4fe370447e,
          and refreshed to apply cleanly to libiscsi.c]

Link: https://lore.kernel.org/r/20220310015759.3296841-4-haowenchao@huawei.com
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Wenchao Hao <haowenchao@huawei.com>
Signed-off-by: Wu Bo <wubo40@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Lee Duncan <lduncan@suse.com>
---
 drivers/scsi/libiscsi.c             |    4 +++-
 drivers/scsi/scsi_transport_iscsi.c |   27 +++++----------------------
 include/scsi/scsi_transport_iscsi.h |    1 -
 3 files changed, 8 insertions(+), 24 deletions(-)

--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -3113,6 +3113,8 @@ void iscsi_conn_teardown(struct iscsi_cl
 	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);
 
 	mutex_lock(&session->eh_mutex);
@@ -3143,7 +3145,7 @@ void iscsi_conn_teardown(struct iscsi_cl
 	spin_unlock_bh(&session->frwd_lock);
 	mutex_unlock(&session->eh_mutex);
 
-	iscsi_destroy_conn(cls_conn);
+	iscsi_put_conn(cls_conn);
 	kfree(tmp_persistent_address);
 	kfree(tmp_local_ipaddr);
 }
--- a/drivers/scsi/scsi_transport_iscsi.c
+++ b/drivers/scsi/scsi_transport_iscsi.c
@@ -2165,7 +2165,11 @@ static int iscsi_iter_destroy_conn_fn(st
 {
 	if (!iscsi_is_conn_dev(dev))
 		return 0;
-	return iscsi_destroy_conn(iscsi_dev_to_conn(dev));
+
+	iscsi_remove_conn(iscsi_dev_to_conn(dev));
+	iscsi_put_conn(iscsi_dev_to_conn(dev));
+
+	return 0;
 }
 
 void iscsi_remove_session(struct iscsi_cls_session *session)
@@ -2437,27 +2441,6 @@ void iscsi_remove_conn(struct iscsi_cls_
 }
 EXPORT_SYMBOL_GPL(iscsi_remove_conn);
 
-/**
- * iscsi_destroy_conn - destroy iscsi class connection
- * @conn: iscsi cls session
- *
- * This can be called from a LLD or iscsi_transport.
- */
-int iscsi_destroy_conn(struct iscsi_cls_conn *conn)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&connlock, flags);
-	list_del(&conn->conn_list);
-	spin_unlock_irqrestore(&connlock, flags);
-
-	transport_unregister_device(&conn->dev);
-	ISCSI_DBG_TRANS_CONN(conn, "Completing conn destruction\n");
-	device_unregister(&conn->dev);
-	return 0;
-}
-EXPORT_SYMBOL_GPL(iscsi_destroy_conn);
-
 void iscsi_put_conn(struct iscsi_cls_conn *conn)
 {
 	put_device(&conn->dev);
--- a/include/scsi/scsi_transport_iscsi.h
+++ b/include/scsi/scsi_transport_iscsi.h
@@ -447,7 +447,6 @@ extern int iscsi_add_conn(struct iscsi_c
 extern void iscsi_remove_conn(struct iscsi_cls_conn *conn);
 extern void iscsi_put_conn(struct iscsi_cls_conn *conn);
 extern void iscsi_get_conn(struct iscsi_cls_conn *conn);
-extern int iscsi_destroy_conn(struct iscsi_cls_conn *conn);
 extern void iscsi_unblock_session(struct iscsi_cls_session *session);
 extern void iscsi_block_session(struct iscsi_cls_session *session);
 extern int iscsi_scan_finished(struct Scsi_Host *shost, unsigned long time);