Patch "target: Fix race between iscsi-target connection shutdown + ABORT_TASK" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

target: Fix race between iscsi-target connection shutdown + ABORT_TASK

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
target-fix-race-between-iscsi-target-connection-shutdown-abort_task.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Nicholas Bellinger <[email protected]>
Date: Thu, 2 Jun 2016 14:56:45 -0700
Subject: target: Fix race between iscsi-target connection shutdown + ABORT_TASK

From: Nicholas Bellinger <[email protected]>

commit 064cdd2d91c2805d788876082f31cc63506f22c3 upstream.

This patch fixes a race in iscsit_release_commands_from_conn() -> iscsit_free_cmd() -> transport_generic_free_cmd() + wait_for_tasks=1, where CMD_T_FABRIC_STOP could end up being set after the final kref_put() is called from core_tmr_abort_task() context.

This results in transport_generic_free_cmd() blocking indefinately on se_cmd->cmd_wait_comp, because the target_release_cmd_kref() check for CMD_T_FABRIC_STOP returns false.

To address this bug, make iscsit_release_commands_from_conn() do list_splice and set CMD_T_FABRIC_STOP early while holding iscsi_conn->cmd_lock. Also make iscsit_aborted_task() only remove iscsi_cmd_t if CMD_T_FABRIC_STOP has not already been set.

Finally in target_release_cmd_kref(), only honor fabric_stop if CMD_T_ABORTED has been set.

---
 drivers/target/iscsi/iscsi_target.c    |   22 ++++++++++++++++------
 drivers/target/target_core_transport.c |    3 ++-
 2 files changed, 18 insertions(+), 7 deletions(-)

@@ -492,7 +492,8 @@ static void iscsit_aborted_task(struct i
 	bool scsi_cmd = (cmd->iscsi_opcode == ISCSI_OP_SCSI_CMD);
 
 	spin_lock_bh(&conn->cmd_lock);
-	if (!list_empty(&cmd->i_conn_node))
+	if (!list_empty(&cmd->i_conn_node) &&
+	    !(cmd->se_cmd.transport_state & CMD_T_FABRIC_STOP))
 		list_del_init(&cmd->i_conn_node);
 	spin_unlock_bh(&conn->cmd_lock);
 

@@ -4194,6 +4195,7 @@ transport_err:
 
 static void iscsit_release_commands_from_conn(struct iscsi_conn *conn)
 {
+	LIST_HEAD(tmp_list);
 	struct iscsi_cmd *cmd = NULL, *cmd_tmp = NULL;
 	struct iscsi_session *sess = conn->sess;
 	/*

@@ -4202,18 +4204,26 @@ static void iscsit_release_commands_from
 	 * has been reset -> returned sleeping pre-handler state.
 	 */
 	spin_lock_bh(&conn->cmd_lock);
-	list_for_each_entry_safe(cmd, cmd_tmp, &conn->conn_cmd_list, i_conn_node) {
+	list_splice_init(&conn->conn_cmd_list, &tmp_list);
 
+	list_for_each_entry(cmd, &tmp_list, i_conn_node) {
+		struct se_cmd *se_cmd = &cmd->se_cmd;
+
+		if (se_cmd->se_tfo != NULL) {
+			spin_lock(&se_cmd->t_state_lock);
+			se_cmd->transport_state |= CMD_T_FABRIC_STOP;
+			spin_unlock(&se_cmd->t_state_lock);
+		}
+	}
+	spin_unlock_bh(&conn->cmd_lock);
+
+	list_for_each_entry_safe(cmd, cmd_tmp, &tmp_list, i_conn_node) {
 		list_del_init(&cmd->i_conn_node);
-		spin_unlock_bh(&conn->cmd_lock);
 
 		iscsit_increment_maxcmdsn(cmd, sess);
-
 		iscsit_free_cmd(cmd, true);
 
-		spin_lock_bh(&conn->cmd_lock);
 	}
-	spin_unlock_bh(&conn->cmd_lock);
 }
 
 static void iscsit_stop_timers_for_cmds(

@@ -2543,7 +2543,8 @@ static void target_release_cmd_kref(stru
 	spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
 
 	spin_lock(&se_cmd->t_state_lock);
-	fabric_stop = (se_cmd->transport_state & CMD_T_FABRIC_STOP);
+	fabric_stop = (se_cmd->transport_state & CMD_T_FABRIC_STOP) &&
+		      (se_cmd->transport_state & CMD_T_ABORTED);
 	spin_unlock(&se_cmd->t_state_lock);
 
 	if (se_cmd->cmd_wait_set || fabric_stop) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/target-fix-max_unmap_lba_count-calc-overflow.patch queue-4.4/target-fix-ordered-task-check_condition-early-exception-handling.patch queue-4.4/target-fix-race-between-iscsi-target-connection-shutdown-abort_task.patch queue-4.4/target-fix-ordered-task-target_setup_cmd_from_cdb-exception-hang.patch queue-4.4/iscsi-target-fix-panic-when-adding-second-tcp-connection-to-iscsi-session.patch queue-4.4/target-fix-missing-complete-during-abort_task-cmd_t_fabric_stop.patch