[PATCH AUTOSEL 5.4 20/23] scsi: target: iscsi: Fix cmd abort fabric stop race

[Sasha Levin <sashal@xxxxxxxxxx>]

From: Mike Christie <michael.christie@xxxxxxxxxx>

[ Upstream commit f36199355c64a39fe82cfddc7623d827c7e050da ]

Maurizio found a race where the abort and cmd stop paths can race as
follows:

 1. thread1 runs iscsit_release_commands_from_conn and sets
    CMD_T_FABRIC_STOP.

 2. thread2 runs iscsit_aborted_task and then does __iscsit_free_cmd. It
    then returns from the aborted_task callout and we finish
    target_handle_abort and do:

    target_handle_abort -> transport_cmd_check_stop_to_fabric ->
	lio_check_stop_free -> target_put_sess_cmd

    The cmd is now freed.

 3. thread1 now finishes iscsit_release_commands_from_conn and runs
    iscsit_free_cmd while accessing a command we just released.

In __target_check_io_state we check for CMD_T_FABRIC_STOP and set the
CMD_T_ABORTED if the driver is not cleaning up the cmd because of a session
shutdown. However, iscsit_release_commands_from_conn only sets the
CMD_T_FABRIC_STOP and does not check to see if the abort path has claimed
completion ownership of the command.

This adds a check in iscsit_release_commands_from_conn so only the abort or
fabric stop path cleanup the command.

Link: https://lore.kernel.org/r/1605318378-9269-1-git-send-email-michael.christie@xxxxxxxxxx
Reported-by: Maurizio Lombardi <mlombard@xxxxxxxxxx>
Reviewed-by: Maurizio Lombardi <mlombard@xxxxxxxxxx>
Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/target/iscsi/iscsi_target.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index bca183369ad8b..3403667a9592f 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -483,8 +483,7 @@ EXPORT_SYMBOL(iscsit_queue_rsp);
 void iscsit_aborted_task(struct iscsi_conn *conn, struct iscsi_cmd *cmd)
 {
 	spin_lock_bh(&conn->cmd_lock);
-	if (!list_empty(&cmd->i_conn_node) &&
-	    !(cmd->se_cmd.transport_state & CMD_T_FABRIC_STOP))
+	if (!list_empty(&cmd->i_conn_node))
 		list_del_init(&cmd->i_conn_node);
 	spin_unlock_bh(&conn->cmd_lock);
 
@@ -4082,12 +4081,22 @@ static void iscsit_release_commands_from_conn(struct iscsi_conn *conn)
 	spin_lock_bh(&conn->cmd_lock);
 	list_splice_init(&conn->conn_cmd_list, &tmp_list);
 
-	list_for_each_entry(cmd, &tmp_list, i_conn_node) {
+	list_for_each_entry_safe(cmd, cmd_tmp, &tmp_list, i_conn_node) {
 		struct se_cmd *se_cmd = &cmd->se_cmd;
 
 		if (se_cmd->se_tfo != NULL) {
 			spin_lock_irq(&se_cmd->t_state_lock);
-			se_cmd->transport_state |= CMD_T_FABRIC_STOP;
+			if (se_cmd->transport_state & CMD_T_ABORTED) {
+				/*
+				 * LIO's abort path owns the cleanup for this,
+				 * so put it back on the list and let
+				 * aborted_task handle it.
+				 */
+				list_move_tail(&cmd->i_conn_node,
+					       &conn->conn_cmd_list);
+			} else {
+				se_cmd->transport_state |= CMD_T_FABRIC_STOP;
+			}
 			spin_unlock_irq(&se_cmd->t_state_lock);
 		}
 	}
-- 
2.27.0