Patch "iscsi-target: Fix TMR reference leak during session shutdown" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

iscsi-target: Fix TMR reference leak during session shutdown

to the 4.9-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:
iscsi-target-fix-tmr-reference-leak-during-session-shutdown.patch
and it can be found in the queue-4.9 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: Thu, 23 Mar 2017 17:19:24 -0700
Subject: iscsi-target: Fix TMR reference leak during session shutdown

From: Nicholas Bellinger <[email protected]>

commit efb2ea770bb3b0f40007530bc8b0c22f36e1c5eb upstream.

This patch fixes a iscsi-target specific TMR reference leak during session shutdown, that could occur when a TMR was quiesced before the hand-off back to iscsi-target code via transport_cmd_check_stop_to_fabric().

The reference leak happens because iscsit_free_cmd() was incorrectly skipping the final target_put_sess_cmd() for TMRs when transport_generic_free_cmd() returned zero because the se_cmd->cmd_kref did not reach zero, due to the missing se_cmd assignment in original code.

The result was iscsi_cmd and it's associated se_cmd memory would be freed once se_sess->sess_cmd_map where released, but the associated se_tmr_req was leaked and remained part of se_device->dev_tmr_list.

This bug would manfiest itself as kernel paging request OOPsen in core_tmr_lun_reset(), when a left-over se_tmr_req attempted to dereference it's se_cmd pointer that had already been released during normal session shutdown.

To address this bug, go ahead and treat ISCSI_OP_SCSI_CMD and ISCSI_OP_SCSI_TMFUNC the same when there is an extra se_cmd->cmd_kref to drop in iscsit_free_cmd(), and use op_scsi to signal __iscsit_free_cmd() when the former needs to clear any further iscsi related I/O state.

---
 drivers/target/iscsi/iscsi_target_util.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

@@ -735,21 +735,23 @@ void iscsit_free_cmd(struct iscsi_cmd *c
 {
 	struct se_cmd *se_cmd = NULL;
 	int rc;
+	bool op_scsi = false;
 	/*
 	 * Determine if a struct se_cmd is associated with
 	 * this struct iscsi_cmd.
 	 */
 	switch (cmd->iscsi_opcode) {
 	case ISCSI_OP_SCSI_CMD:
-		se_cmd = &cmd->se_cmd;
-		__iscsit_free_cmd(cmd, true, shutdown);
+		op_scsi = true;
 		/*
 		 * Fallthrough
 		 */
 	case ISCSI_OP_SCSI_TMFUNC:
-		rc = transport_generic_free_cmd(&cmd->se_cmd, shutdown);
-		if (!rc && shutdown && se_cmd && se_cmd->se_sess) {
-			__iscsit_free_cmd(cmd, true, shutdown);
+		se_cmd = &cmd->se_cmd;
+		__iscsit_free_cmd(cmd, op_scsi, shutdown);
+		rc = transport_generic_free_cmd(se_cmd, shutdown);
+		if (!rc && shutdown && se_cmd->se_sess) {
+			__iscsit_free_cmd(cmd, op_scsi, shutdown);
 			target_put_sess_cmd(se_cmd);
 		}
 		break;

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

queue-4.9/tcmu-fix-wrongly-calculating-of-the-base_command_size.patch queue-4.9/iscsi-target-drop-work-around-for-legacy-globalsan-initiator.patch queue-4.9/iscsi-target-fix-tmr-reference-leak-during-session-shutdown.patch queue-4.9/target-avoid-mappedlun-symlink-creation-during-lun-shutdown.patch queue-4.9/tcmu-fix-possible-overwrite-of-t_data_sg-s-last-iov.patch queue-4.9/tcmu-skip-data-out-blocks-before-gathering-data-in-buffer-for-bidi-case.patch