[PATCH v2 3/3] scsi: target: iscsi: don't re-arm Time2Retain on a closing session

[Daniel Wade <danjwade95@gmail.com>]

iscsi_target_login_sess_out() re-arms the Time2Retain timer of the
session whose login just failed.  In the window closed by the previous
patch that session may already be on its way out: iscsit_close_session()
stops that timer, then sleeps in iscsit_check_session_usage_count() on
the reference this path is about to drop, and frees the session as soon
as it is dropped.  A re-arm therefore lands between the stop and the
free, and leaves an armed timer on freed memory.

->session_close is set before the free is committed to, so test it here
too and skip the re-arm.

Unlike the previous patch this does not need the other teardown flags.
Every iscsit_close_session() that reaches the free is the can_sleep=true
call from iscsit_close_connection() and has ->session_close set, while
iscsit_handle_time2retain_timeout() passes false and re-arms the timer
instead of freeing when a usage count is held.

Fixes: e48354ce078c ("iscsi-target: Add iSCSI fabric support for target v4.1")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Wade <danjwade95@gmail.com>
---
 drivers/target/iscsi/iscsi_target_login.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
index 556ae5d2d50..124c9903fac 100644
--- a/drivers/target/iscsi/iscsi_target_login.c
+++ b/drivers/target/iscsi/iscsi_target_login.c
@@ -1177,7 +1177,13 @@ void iscsi_target_login_sess_out(struct iscsit_conn *conn,
 	 */
 	if (!zero_tsih && conn->sess) {
 		spin_lock_bh(&conn->sess->conn_lock);
-		if (conn->sess->session_state == TARG_SESS_STATE_FAILED) {
+		/*
+		 * iscsit_close_session() stopped this timer before sleeping on
+		 * the usage count this path drops, so re-arming it would leave
+		 * the timer armed on freed memory.
+		 */
+		if (conn->sess->session_state == TARG_SESS_STATE_FAILED &&
+		    !atomic_read(&conn->sess->session_close)) {
 			struct se_portal_group *se_tpg =
 					&conn->tpg->tpg_se_tpg;
 
-- 
2.39.0.windows.2