Commit 97b52957 authored Nov 13, 2020 by Mike Christie Committed by Greg Kroah-Hartman Dec 02, 2020

scsi: target: iscsi: Fix cmd abort fabric stop race

[ 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@oracle.com


Reported-by: Maurizio Lombardi <mlombard@redhat.com>
Reviewed-by: Maurizio Lombardi <mlombard@redhat.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent e0172455

drivers/target/iscsi/iscsi_target.c

+13 −4

Original line number	Diff line number	Diff line
		@@ -492,8 +492,7 @@ 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);

		@@ -4054,12 +4053,22 @@ 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);
		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);
		}
		}