linux-kernel - [PATCH 4.14 116/193] target: Fix caw_sem leak in transport_generic_request

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Date:   Tue, 28 Nov 2017 11:26:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mike Christie <mchristi@...hat.com>,
        Hannes Reinecke <hare@...e.com>,
        Bart Van Assche <bart.vanassche@...disk.com>,
        Nicholas Bellinger <nab@...ux-iscsi.org>
Subject: [PATCH 4.14 116/193] target: Fix caw_sem leak in transport_generic_request_failure

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Bellinger <nab@...ux-iscsi.org>

commit fd2f928b0ddd2fe8876d4f1344df2ace2b715a4d upstream.

With the recent addition of transport_check_aborted_status() within
transport_generic_request_failure() to avoid sending a SCSI status
exception after CMD_T_ABORTED w/ TAS=1 has occured, it introduced
a COMPARE_AND_WRITE early failure regression.

Namely when COMPARE_AND_WRITE fails and se_device->caw_sem has
been taken by sbc_compare_and_write(), if the new check for
transport_check_aborted_status() returns true and exits,
cmd->transport_complete_callback() -> compare_and_write_post()
is skipped never releasing se_device->caw_sem.

This regression was originally introduced by:

  commit e3b88ee95b4e4bf3e9729a4695d695b9c7c296c8
  Author: Bart Van Assche <bart.vanassche@...disk.com>
  Date:   Tue Feb 14 16:25:45 2017 -0800

      target: Fix handling of aborted failed commands

To address this bug, move the transport_check_aborted_status()
call after transport_complete_task_attr() and
cmd->transport_complete_callback().

Cc: Mike Christie <mchristi@...hat.com>
Cc: Hannes Reinecke <hare@...e.com>
Cc: Bart Van Assche <bart.vanassche@...disk.com>
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/target/target_core_transport.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1730,9 +1730,6 @@ void transport_generic_request_failure(s
 {
 	int ret = 0, post_ret = 0;
 
-	if (transport_check_aborted_status(cmd, 1))
-		return;
-
 	pr_debug("-----[ Storage Engine Exception; sense_reason %d\n",
 		 sense_reason);
 	target_show_cmd("-----[ ", cmd);
@@ -1741,6 +1738,7 @@ void transport_generic_request_failure(s
 	 * For SAM Task Attribute emulation for failed struct se_cmd
 	 */
 	transport_complete_task_attr(cmd);
+
 	/*
 	 * Handle special case for COMPARE_AND_WRITE failure, where the
 	 * callback is expected to drop the per device ->caw_sem.
@@ -1749,6 +1747,9 @@ void transport_generic_request_failure(s
 	     cmd->transport_complete_callback)
 		cmd->transport_complete_callback(cmd, false, &post_ret);
 
+	if (transport_check_aborted_status(cmd, 1))
+		return;
+
 	switch (sense_reason) {
 	case TCM_NON_EXISTENT_LUN:
 	case TCM_UNSUPPORTED_SCSI_OPCODE: