Commit 9b2792c3 authored Feb 06, 2017 by Nicholas Bellinger

target: Fix COMPARE_AND_WRITE ref leak for non GOOD status



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.

Reported-by: Donald White <dew@datera.io>
Cc: Donald White <dew@datera.io>
Tested-by: Gary Guo <ghg@datera.io>
Cc: Gary Guo <ghg@datera.io>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: <stable@vger.kernel.org> # v3.12+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

parent 01d4d673

drivers/target/target_core_sbc.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -451,6 +451,7 @@ static sense_reason_t compare_and_write_post(struct se_cmd *cmd, bool success,
		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
		@@ -458,9 +459,12 @@ static sense_reason_t compare_and_write_post(struct se_cmd *cmd, bool success,
		* 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);

		@@ -470,7 +474,7 @@ static sense_reason_t compare_and_write_post(struct se_cmd *cmd, bool success,
		*/
		up(&dev->caw_sem);

		return TCM_NO_SENSE;
		return ret;
		}

		static sense_reason_t compare_and_write_callback(struct se_cmd *cmd, bool success,