[PATCH AUTOSEL 4.19 13/15] scsi: target: iscsi: Fix cmd abort fabric stop race

Sasha Levin
2020-11-25T15:38:34Z

From: Mike Christie <michael.christie@oracle.com>

[ 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>
---
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 2602b57936d4b..58ccded1be857 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -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);
- 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