[PATCH 3.16.y-ckt 061/144] iscsi-target: Avoid early conn_logout_comp for iser connections

[Luis Henriques]

3.16.7-ckt10 -stable review patch.  If anyone has any objections, please let me know.

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

From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>

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@xxxxxxxxxxxx>
Cc: Sagi Grimberg <sagig@xxxxxxxxxxxx>
Cc: Slava Shwartsman <valyushash@xxxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 drivers/target/iscsi/iscsi_target.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 260c3e1e312c..209eb58b5d3a 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -4223,11 +4223,17 @@ 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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