linux-kernel - [PATCH 3.14 74/79] iscsi-target: Avoid early conn_logout

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Message-Id: <20150324154424.866245811@linuxfoundation.org>
Date:	Tue, 24 Mar 2015 16:46:25 +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, Sagi Grimberg <sagig@...lanox.com>,
	Slava Shwartsman <valyushash@...il.com>,
	Nicholas Bellinger <nab@...ux-iscsi.org>
Subject: [PATCH 3.14 74/79] iscsi-target: Avoid early conn_logout_comp for iser connections

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

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

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

commit f068fbc82e7696d67b1bb8189306865bedf368b6 upstream.

This patch fixes a iser specific logout bug where early complete()
of conn->conn_logout_comp in iscsit_close_connection() was causing
isert_wait4logout() to complete too soon, triggering a use after
free NULL pointer dereference of iscsi_conn memory.

The complete() was originally added for traditional iscsi-target
when a ISCSI_LOGOUT_OP failed in iscsi_target_rx_opcode(), but given
iser-target does not wait in logout failure, this special case needs
to be avoided.

Reported-by: Sagi Grimberg <sagig@...lanox.com>
Cc: Sagi Grimberg <sagig@...lanox.com>
Cc: Slava Shwartsman <valyushash@...il.com>
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/target/iscsi/iscsi_target.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -4196,11 +4196,17 @@ int iscsit_close_connection(
 	pr_debug("Closing iSCSI connection CID %hu on SID:"
 		" %u\n", conn->cid, sess->sid);
 	/*
-	 * Always up conn_logout_comp just in case the RX Thread is sleeping
-	 * and the logout response never got sent because the connection
-	 * failed.
+	 * Always up conn_logout_comp for the traditional TCP case just in case
+	 * the RX Thread in iscsi_target_rx_opcode() is sleeping and the logout
+	 * response never got sent because the connection failed.
+	 *
+	 * However for iser-target, isert_wait4logout() is using conn_logout_comp
+	 * to signal logout response TX interrupt completion.  Go ahead and skip
+	 * this for iser since isert_rx_opcode() does not wait on logout failure,
+	 * and to avoid iscsi_conn pointer dereference in iser-target code.
 	 */
-	complete(&conn->conn_logout_comp);
+	if (conn->conn_transport->transport_type == ISCSI_TCP)
+		complete(&conn->conn_logout_comp);
 
 	iscsi_release_thread_set(conn);
 


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