[2/2] target: Fix LUN_RESET active TMR descriptor handling

Commit Message

Nicholas A. Bellinger Jan. 12, 2016, 10:24 a.m. UTC

From: Nicholas Bellinger <[e-mail]>

This patch fixes a NULL pointer se_cmd->cmd_kref < 0
refcount bug during TMR LUN_RESET with TMR se_cmd,
triggered during se_cmd + se_tmr_req descriptor
shutdown + release via core_tmr_drain_tmr_list().

It obtains kref_get_unless_zero(&se_cmd->cmd_kref)
following __target_check_io_state() for active I/O
CMD_T_ABORTED, and adds transport_wait_for_tasks()
followed by the final target_put_sess_cmd() to
release TMR logic locally obtained ->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_empty() + list_del_init() ahead of
se_tmr_req memory free.

Cc: Quinn Tran <[e-mail]>
Cc: Himanshu Madhani <[e-mail]>
Cc: Sagi Grimberg <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: Hannes Reinecke <[e-mail]>
Cc: Andy Grover <[e-mail]>
Signed-off-by: Nicholas Bellinger <[e-mail]>
---
 drivers/target/target_core_tmr.c       | 24 +++++++++++++++++++++++-
 drivers/target/target_core_transport.c | 17 +++++++++++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)

Comments

Christoph Hellwig Jan. 12, 2016, 3:25 p.m. UTC | #1

>  	if (dev) {
>  		spin_lock_irqsave(&dev->se_tmr_lock, flags);
> -		list_del(&tmr->tmr_list);
> +		if (!list_empty(&tmr->tmr_list))
> +			list_del_init(&tmr->tmr_list);

list_del_init on a empty list is fine.

> +		sess = cmd->se_sess;
> +		if (!sess) {
> +			dump_stack();
> +			continue;
> +		}

Why not something like:

		if (WARN_ON_ONCE(!sess))
			continue;

same for the previous patch.

> +		spin_lock(&sess->sess_cmd_lock);
> +		rc = kref_get_unless_zero(&cmd->cmd_kref);
> +		spin_unlock(&sess->sess_cmd_lock);

no need to take a lock around kref_get_unless_zero, it's not going to
help with anything.
--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to [e-mail]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Nicholas A. Bellinger Jan. 23, 2016, 2:02 a.m. UTC | #2

On Tue, 2016-01-12 at 16:25 +0100, Christoph Hellwig wrote:
> >  	if (dev) {
> >  		spin_lock_irqsave(&dev->se_tmr_lock, flags);
> > -		list_del(&tmr->tmr_list);
> > +		if (!list_empty(&tmr->tmr_list))
> > +			list_del_init(&tmr->tmr_list);
> 
> list_del_init on a empty list is fine.
> 

Done.

> > +		sess = cmd->se_sess;
> > +		if (!sess) {
> > +			dump_stack();
> > +			continue;
> > +		}
> 
> Why not something like:
> 
> 		if (WARN_ON_ONCE(!sess))
> 			continue;
> 
> same for the previous patch.
> 

Done.

> > +		spin_lock(&sess->sess_cmd_lock);
> > +		rc = kref_get_unless_zero(&cmd->cmd_kref);
> > +		spin_unlock(&sess->sess_cmd_lock);
> 
> no need to take a lock around kref_get_unless_zero, it's not going to
> help with anything.

So for -v2, this lock is being obtained before ->t_state_lock above, to
follow how __target_check_io_state() works with aborted I/O + LUN_RESET
and explicit TMR_ABORT_TASK.

It's been made consistent with the other cases for now, but depending on
how the bug-fix for se_session shutdown plus remote port LUN_RESET works
out, this may or may-not be able to go away for -v3.

--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to [e-mail]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/drivers/target/target_core_tmr.c b/drivers/target/target_core_tmr.c
index af4adb6..894a0b0 100644
--- a/drivers/target/target_core_tmr.c
+++ b/drivers/target/target_core_tmr.c
@@ -68,7 +68,8 @@  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);
+		if (!list_empty(&tmr->tmr_list))
+			list_del_init(&tmr->tmr_list);
 		spin_unlock_irqrestore(&dev->se_tmr_lock, flags);
 	}
 
@@ -192,9 +193,12 @@  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..
@@ -220,6 +224,12 @@  static void core_tmr_drain_tmr_list(
 		if (target_check_cdb_and_preempt(preempt_and_abort_list, cmd))
 			continue;
 
+		sess = cmd->se_sess;
+		if (!sess) {
+			dump_stack();
+			continue;
+		}
+
 		spin_lock(&cmd->t_state_lock);
 		if (!(cmd->transport_state & CMD_T_ACTIVE)) {
 			spin_unlock(&cmd->t_state_lock);
@@ -229,8 +239,16 @@  static void core_tmr_drain_tmr_list(
 			spin_unlock(&cmd->t_state_lock);
 			continue;
 		}
+		cmd->transport_state |= CMD_T_ABORTED;
 		spin_unlock(&cmd->t_state_lock);
 
+		spin_lock(&sess->sess_cmd_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);
@@ -244,7 +262,11 @@  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 f2c596b..f6ecb60 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -2905,8 +2905,17 @@  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);
@@ -2939,9 +2948,17 @@  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);
 }