Patch "target: Fix COMPARE_AND_WRITE ref leak for non GOOD status" 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 COMPARE_AND_WRITE ref leak for non GOOD status

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-compare_and_write-ref-leak-for-non-good-status.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: Mon, 6 Feb 2017 14:28:09 -0800
Subject: target: Fix COMPARE_AND_WRITE ref leak for non GOOD status

From: Nicholas Bellinger <[email protected]>

commit 9b2792c3da1e80f2d460167d319302a24c9ca2b7 upstream.

This patch addresses a long standing bug where the commit phase of COMPARE_AND_WRITE would result in a se_cmd->cmd_kref reference leak if se_cmd->scsi_status returned non SAM_STAT_GOOD.

This would manifest first as a lost SCSI response, and eventual hung task during fabric driver logout or re-login, as existing shutdown logic waited for the COMPARE_AND_WRITE se_cmd->cmd_kref to reach zero.

To address this bug, compare_and_write_post() has been changed to drop the incorrect !cmd->scsi_status conditional that was preventing *post_ret = 1 for being set during non SAM_STAT_GOOD status.

This patch has been tested with SAM_STAT_CHECK_CONDITION status from normal target_complete_cmd() callback path, as well as the incoming __target_execute_cmd() submission failure path when se_cmd->execute_cmd() returns non zero status.

---
 drivers/target/target_core_sbc.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

@@ -442,6 +442,7 @@ static sense_reason_t compare_and_write_
 					     int *post_ret)
 {
 	struct se_device *dev = cmd->se_dev;
+	sense_reason_t ret = TCM_NO_SENSE;
 
 	/*
 	 * Only set SCF_COMPARE_AND_WRITE_POST to force a response fall-through

@@ -449,9 +450,12 @@ static sense_reason_t compare_and_write_
 	 * sent to the backend driver.
 	 */
 	spin_lock_irq(&cmd->t_state_lock);
-	if ((cmd->transport_state & CMD_T_SENT) && !cmd->scsi_status) {
+	if (cmd->transport_state & CMD_T_SENT) {
 		cmd->se_cmd_flags |= SCF_COMPARE_AND_WRITE_POST;
 		*post_ret = 1;
+
+		if (cmd->scsi_status == SAM_STAT_CHECK_CONDITION)
+			ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 	}
 	spin_unlock_irq(&cmd->t_state_lock);
 

@@ -461,7 +465,7 @@ static sense_reason_t compare_and_write_
 	 */
 	up(&dev->caw_sem);
 
-	return TCM_NO_SENSE;
+	return ret;
 }
 
 static sense_reason_t compare_and_write_callback(struct se_cmd *cmd, bool success,

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

queue-4.4/target-fix-compare_and_write-ref-leak-for-non-good-status.patch queue-4.4/target-use-correct-scsi-status-during-extended_copy-exception.patch queue-4.4/target-don-t-bug_on-during-nodeacl-dynamic-explicit-conversion.patch queue-4.4/target-fix-early-transport_generic_handle_tmr-abort-scenario.patch