linux-kernel - [PATCH 3.10 232/268] iscsi-target: Fix TMR reference leak during session shutdown

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Message-Id: <1497897167-14556-233-git-send-email-w@1wt.eu>
Date:   Mon, 19 Jun 2017 20:32:11 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Nicholas Bellinger <nab@...ux-iscsi.org>,
        Rob Millner <rlm@...erainc.com>, Chu Yuan Lin <cyl@...era.io>,
        Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 232/268] iscsi-target: Fix TMR reference leak during session shutdown

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

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.

Reported-by: Rob Millner <rlm@...erainc.com>
Cc: Rob Millner <rlm@...erainc.com>
Reported-by: Chu Yuan Lin <cyl@...era.io>
Cc: Chu Yuan Lin <cyl@...era.io>
Tested-by: Chu Yuan Lin <cyl@...era.io>
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/target/iscsi/iscsi_target_util.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c
index 016e882..eeeea38 100644
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -722,21 +722,23 @@ void iscsit_free_cmd(struct iscsi_cmd *cmd, bool shutdown)
 {
 	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->se_sess, se_cmd);
 		}
 		break;
-- 
2.8.0.rc2.1.gbe9624a