[Devel] [PATCH RHEL7 COMMIT] ms/target: Fix LUN_RESET active TMR descriptor handling

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-693.21.1.vz7.46.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.21.1.vz7.46.2
------>
commit 73d0dab0653d855435df9492b0724e480d5415ab
Author: Nicholas Bellinger <nab at linux-iscsi.org>
Date:   Mon Apr 2 17:28:27 2018 +0300

    ms/target: Fix LUN_RESET active TMR descriptor handling
    
    ML: a6d9bb1c9605cd4f44e2d8290dc4d0e88f20292d
    
    This patch fixes a NULL pointer se_cmd->cmd_kref < 0
    refcount bug during TMR LUN_RESET with active TMRs,
    triggered during se_cmd + se_tmr_req descriptor
    shutdown + release via core_tmr_drain_tmr_list().
    
    To address this bug, go ahead and obtain a local
    kref_get_unless_zero(&se_cmd->cmd_kref) for active I/O
    to set CMD_T_ABORTED, and transport_wait_for_tasks()
    followed by the final target_put_sess_cmd() to drop
    the local ->cmd_kref.
    
    Also add two new checks within target_tmr_work() to
    avoid CMD_T_ABORTED -> TFO->queue_tm_rsp() callbacks
    ahead of invoking the backend -> fabric put in
    transport_cmd_check_stop_to_fabric().
    
    For good measure, also change core_tmr_release_req()
    to use list_del_init() ahead of se_tmr_req memory
    free.
    
    Reviewed-by: Quinn Tran <quinn.tran at qlogic.com>
    Cc: Himanshu Madhani <himanshu.madhani at qlogic.com>
    Cc: Sagi Grimberg <sagig at mellanox.com>
    Cc: Christoph Hellwig <hch at lst.de>
    Cc: Hannes Reinecke <hare at suse.de>
    Cc: Andy Grover <agrover at redhat.com>
    Cc: Mike Christie <mchristi at redhat.com>
    Cc: stable at vger.kernel.org # 3.10+
    Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
    Signed-off-by: Andrei Vagin <avagin at openvz.org>
---
 drivers/target/target_core_tmr.c       | 22 +++++++++++++++++++++-
 drivers/target/target_core_transport.c | 17 +++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/drivers/target/target_core_tmr.c b/drivers/target/target_core_tmr.c
index e2c96725a7bf..99bc3d4db737 100644
--- a/drivers/target/target_core_tmr.c
+++ b/drivers/target/target_core_tmr.c
@@ -71,7 +71,7 @@ void core_tmr_release_req(struct se_tmr_req *tmr)
 
 	if (dev) {
 		spin_lock_irqsave(&dev->se_tmr_lock, flags);
-		list_del(&tmr->tmr_list);
+		list_del_init(&tmr->tmr_list);
 		spin_unlock_irqrestore(&dev->se_tmr_lock, flags);
 	}
 
@@ -202,9 +202,11 @@ static void core_tmr_drain_tmr_list(
 	struct list_head *preempt_and_abort_list)
 {
 	LIST_HEAD(drain_tmr_list);
+	struct se_session *sess;
 	struct se_tmr_req *tmr_p, *tmr_pp;
 	struct se_cmd *cmd;
 	unsigned long flags;
+	bool rc;
 	/*
 	 * Release all pending and outgoing TMRs aside from the received
 	 * LUN_RESET tmr..
@@ -230,17 +232,31 @@ static void core_tmr_drain_tmr_list(
 		if (target_check_cdb_and_preempt(preempt_and_abort_list, cmd))
 			continue;
 
+		sess = cmd->se_sess;
+		if (WARN_ON_ONCE(!sess))
+			continue;
+
+		spin_lock(&sess->sess_cmd_lock);
 		spin_lock(&cmd->t_state_lock);
 		if (!(cmd->transport_state & CMD_T_ACTIVE)) {
 			spin_unlock(&cmd->t_state_lock);
+			spin_unlock(&sess->sess_cmd_lock);
 			continue;
 		}
 		if (cmd->t_state == TRANSPORT_ISTATE_PROCESSING) {
 			spin_unlock(&cmd->t_state_lock);
+			spin_unlock(&sess->sess_cmd_lock);
 			continue;
 		}
+		cmd->transport_state |= CMD_T_ABORTED;
 		spin_unlock(&cmd->t_state_lock);
 
+		rc = kref_get_unless_zero(&cmd->cmd_kref);
+		spin_unlock(&sess->sess_cmd_lock);
+		if (!rc) {
+			printk("LUN_RESET TMR: non-zero kref_get_unless_zero\n");
+			continue;
+		}
 		list_move_tail(&tmr_p->tmr_list, &drain_tmr_list);
 	}
 	spin_unlock_irqrestore(&dev->se_tmr_lock, flags);
@@ -254,7 +270,11 @@ static void core_tmr_drain_tmr_list(
 			(preempt_and_abort_list) ? "Preempt" : "", tmr_p,
 			tmr_p->function, tmr_p->response, cmd->t_state);
 
+		cancel_work_sync(&cmd->work);
+		transport_wait_for_tasks(cmd);
+
 		transport_cmd_finish_abort(cmd, 1);
+		target_put_sess_cmd(cmd);
 	}
 }
 
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 1a6ebd20e3bc..92dad1cc4034 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -2949,8 +2949,17 @@ static void target_tmr_work(struct work_struct *work)
 	struct se_cmd *cmd = container_of(work, struct se_cmd, work);
 	struct se_device *dev = cmd->se_dev;
 	struct se_tmr_req *tmr = cmd->se_tmr_req;
+	unsigned long flags;
 	int ret;
 
+	spin_lock_irqsave(&cmd->t_state_lock, flags);
+	if (cmd->transport_state & CMD_T_ABORTED) {
+		tmr->response = TMR_FUNCTION_REJECTED;
+		spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+		goto check_stop;
+	}
+	spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+
 	switch (tmr->function) {
 	case TMR_ABORT_TASK:
 		core_tmr_abort_task(dev, tmr, cmd->se_sess);
@@ -2978,9 +2987,17 @@ static void target_tmr_work(struct work_struct *work)
 		break;
 	}
 
+	spin_lock_irqsave(&cmd->t_state_lock, flags);
+	if (cmd->transport_state & CMD_T_ABORTED) {
+		spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+		goto check_stop;
+	}
 	cmd->t_state = TRANSPORT_ISTATE_PROCESSING;
+	spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+
 	cmd->se_tfo->queue_tm_rsp(cmd);
 
+check_stop:
 	transport_cmd_check_stop_to_fabric(cmd);
 }