linux-kernel - [PATCH 4.8 137/140] target: Re-add missing SCF_ACK

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Message-Id: <20161026122226.332250613@linuxfoundation.org>
Date:   Wed, 26 Oct 2016 14:23:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vaibhav Tandon <vst@...era.io>,
        Nicholas Bellinger <nab@...ux-iscsi.org>
Subject: [PATCH 4.8 137/140] target: Re-add missing SCF_ACK_KREF assignment in v4.1.y

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

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

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

commit 527268df31e57cf2b6d417198717c6d6afdb1e3e upstream.

This patch fixes a regression in >= v4.1.y code where the original
SCF_ACK_KREF assignment in target_get_sess_cmd() was dropped upstream
in commit 054922bb, but the series for addressing TMR ABORT_TASK +
LUN_RESET with fabric session reinstatement in commit febe562c20 still
depends on this code in transport_cmd_finish_abort().

The regression manifests itself as a se_cmd->cmd_kref +1 leak, where
ABORT_TASK + LUN_RESET can hang indefinately for a specific I_T session
for drivers using SCF_ACK_KREF, resulting in hung kthreads.

This patch has been verified with v4.1.y code.

Reported-by: Vaibhav Tandon <vst@...era.io>
Tested-by: Vaibhav Tandon <vst@...era.io>
Cc: Vaibhav Tandon <vst@...era.io>
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -2547,8 +2547,10 @@ int target_get_sess_cmd(struct se_cmd *s
 	 * fabric acknowledgement that requires two target_put_sess_cmd()
 	 * invocations before se_cmd descriptor release.
 	 */
-	if (ack_kref)
+	if (ack_kref) {
 		kref_get(&se_cmd->cmd_kref);
+		se_cmd->se_cmd_flags |= SCF_ACK_KREF;
+	}

 	spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
 	if (se_sess->sess_tearing_down) {