linux-kernel - [PATCH 3.16 096/192] target: Fix COMPARE_AND_WRITE caw_sem leak during se

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Message-ID: <lsq.1507553064.663159680@decadent.org.uk>
Date:   Mon, 09 Oct 2017 13:44:24 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Nicholas Bellinger" <nab@...ux-iscsi.org>,
        "Jiang Yi" <jiangyilism@...il.com>
Subject: [PATCH 3.16 096/192] target: Fix COMPARE_AND_WRITE caw_sem leak
 during se_cmd quiesce

3.16.49-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Jiang Yi <jiangyilism@...il.com>

commit 1d6ef276594a781686058802996e09c8550fd767 upstream.

This patch addresses a COMPARE_AND_WRITE se_device->caw_sem leak,
that would be triggered during normal se_cmd shutdown or abort
via __transport_wait_for_tasks().

This would occur because target_complete_cmd() would catch this
early and do complete_all(&cmd->t_transport_stop_comp), but since
target_complete_ok_work() or target_complete_failure_work() are
never called to invoke se_cmd->transport_complete_callback(),
the COMPARE_AND_WRITE specific callbacks never release caw_sem.

To address this special case, go ahead and release caw_sem
directly from target_complete_cmd().

(Remove '&& success' from check, to release caw_sem regardless
 of scsi_status - nab)

Signed-off-by: Jiang Yi <jiangyilism@...il.com>
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/target/target_core_transport.c | 9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -689,6 +689,15 @@ void target_complete_cmd(struct se_cmd *
 	if (cmd->transport_state & CMD_T_ABORTED ||
 	    cmd->transport_state & CMD_T_STOP) {
 		spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+		/*
+		 * If COMPARE_AND_WRITE was stopped by __transport_wait_for_tasks(),
+		 * release se_device->caw_sem obtained by sbc_compare_and_write()
+		 * since target_complete_ok_work() or target_complete_failure_work()
+		 * won't be called to invoke the normal CAW completion callbacks.
+		 */
+		if (cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE) {
+			up(&dev->caw_sem);
+		}
 		complete_all(&cmd->t_transport_stop_comp);
 		return;
 	} else if (!success) {