scsi: target: iscsi: Fix hang in the iSCSI login code

If the initiator suddenly stops sending data during a login while keeping
the TCP connection open, the login_work won't be scheduled and will never
release the login semaphore; concurrent login operations will therefore get
stuck and fail.

The bug is due to the inability of the login timeout code to properly
handle this particular case.

Fix the problem by replacing the old per-NP login timer with a new
per-connection timer.

The timer is started when an initiator connects to the target; if it
expires, it sends a SIGINT signal to the thread pointed at by the
conn->login_kworker pointer.

conn->login_kworker is set by calling the iscsit_set_login_timer_kworker()
helper, initially it will point to the np thread; When the login
operation's control is in the process of being passed from the NP-thread to
login_work, the conn->login_worker pointer is set to NULL.  Finally,
login_kworker will be changed to point to the worker thread executing the
login_work job.

If conn->login_kworker is NULL when the timer expires, it means that the
login operation hasn't been completed yet but login_work isn't running, in
this case the timer will mark the login process as failed and will schedule
login_work so the latter will be forced to free the resources it holds.

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Link: https://lore.kernel.org/r/20230508162219.1731964-2-mlombard@redhat.com
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/iscsi/iscsi_target.c

@@ -364,8 +364,6 @@ struct iscsi_np *iscsit_add_np(
 	init_completion(&np->np_restart_comp);
 	INIT_LIST_HEAD(&np->np_list);
 
-	timer_setup(&np->np_login_timer, iscsi_handle_login_thread_timeout, 0);
-
 	ret = iscsi_target_setup_login_socket(np, sockaddr);
 	if (ret != 0) {
 		kfree(np);

drivers/target/iscsi/iscsi_target_login.c

@@ -811,59 +811,6 @@ void iscsi_post_login_handler(
 	iscsit_dec_conn_usage_count(conn);
 }
 
-void iscsi_handle_login_thread_timeout(struct timer_list *t)
-{
-	struct iscsi_np *np = from_timer(np, t, np_login_timer);
-
-	spin_lock_bh(&np->np_thread_lock);
-	pr_err("iSCSI Login timeout on Network Portal %pISpc\n",
-			&np->np_sockaddr);
-
-	if (np->np_login_timer_flags & ISCSI_TF_STOP) {
-		spin_unlock_bh(&np->np_thread_lock);
-		return;
-	}
-
-	if (np->np_thread)
-		send_sig(SIGINT, np->np_thread, 1);
-
-	np->np_login_timer_flags &= ~ISCSI_TF_RUNNING;
-	spin_unlock_bh(&np->np_thread_lock);
-}
-
-static void iscsi_start_login_thread_timer(struct iscsi_np *np)
-{
-	/*
-	 * This used the TA_LOGIN_TIMEOUT constant because at this
-	 * point we do not have access to ISCSI_TPG_ATTRIB(tpg)->login_timeout
-	 */
-	spin_lock_bh(&np->np_thread_lock);
-	np->np_login_timer_flags &= ~ISCSI_TF_STOP;
-	np->np_login_timer_flags |= ISCSI_TF_RUNNING;
-	mod_timer(&np->np_login_timer, jiffies + TA_LOGIN_TIMEOUT * HZ);
-
-	pr_debug("Added timeout timer to iSCSI login request for"
-			" %u seconds.\n", TA_LOGIN_TIMEOUT);
-	spin_unlock_bh(&np->np_thread_lock);
-}
-
-static void iscsi_stop_login_thread_timer(struct iscsi_np *np)
-{
-	spin_lock_bh(&np->np_thread_lock);
-	if (!(np->np_login_timer_flags & ISCSI_TF_RUNNING)) {
-		spin_unlock_bh(&np->np_thread_lock);
-		return;
-	}
-	np->np_login_timer_flags |= ISCSI_TF_STOP;
-	spin_unlock_bh(&np->np_thread_lock);
-
-	del_timer_sync(&np->np_login_timer);
-
-	spin_lock_bh(&np->np_thread_lock);
-	np->np_login_timer_flags &= ~ISCSI_TF_RUNNING;
-	spin_unlock_bh(&np->np_thread_lock);
-}
-
 int iscsit_setup_np(
 	struct iscsi_np *np,
 	struct sockaddr_storage *sockaddr)
@@ -1123,10 +1070,13 @@ static struct iscsit_conn *iscsit_alloc_conn(struct iscsi_np *np)
 	spin_lock_init(&conn->nopin_timer_lock);
 	spin_lock_init(&conn->response_queue_lock);
 	spin_lock_init(&conn->state_lock);
+	spin_lock_init(&conn->login_worker_lock);
+	spin_lock_init(&conn->login_timer_lock);
 
 	timer_setup(&conn->nopin_response_timer,
 		    iscsit_handle_nopin_response_timeout, 0);
 	timer_setup(&conn->nopin_timer, iscsit_handle_nopin_timeout, 0);
+	timer_setup(&conn->login_timer, iscsit_login_timeout, 0);
 
 	if (iscsit_conn_set_transport(conn, np->np_transport) < 0)
 		goto free_conn;
@@ -1304,7 +1254,7 @@ static int __iscsi_target_login_thread(struct iscsi_np *np)
 		goto new_sess_out;
 	}
 
-	iscsi_start_login_thread_timer(np);
+	iscsit_start_login_timer(conn, current);
 
 	pr_debug("Moving to TARG_CONN_STATE_XPT_UP.\n");
 	conn->conn_state = TARG_CONN_STATE_XPT_UP;
@@ -1417,8 +1367,6 @@ static int __iscsi_target_login_thread(struct iscsi_np *np)
 	if (ret < 0)
 		goto new_sess_out;
 
-	iscsi_stop_login_thread_timer(np);
-
 	if (ret == 1) {
 		tpg_np = conn->tpg_np;
 
@@ -1434,7 +1382,7 @@ static int __iscsi_target_login_thread(struct iscsi_np *np)
 new_sess_out:
 	new_sess = true;
 old_sess_out:
-	iscsi_stop_login_thread_timer(np);
+	iscsit_stop_login_timer(conn);
 	tpg_np = conn->tpg_np;
 	iscsi_target_login_sess_out(conn, zero_tsih, new_sess);
 	new_sess = false;
@@ -1448,7 +1396,6 @@ static int __iscsi_target_login_thread(struct iscsi_np *np)
 	return 1;
 
 exit:
-	iscsi_stop_login_thread_timer(np);
 	spin_lock_bh(&np->np_thread_lock);
 	np->np_thread_state = ISCSI_NP_THREAD_EXIT;
 	spin_unlock_bh(&np->np_thread_lock);

drivers/target/iscsi/iscsi_target_nego.c

@@ -535,25 +535,6 @@ static void iscsi_target_login_drop(struct iscsit_conn *conn, struct iscsi_login
 	iscsi_target_login_sess_out(conn, zero_tsih, true);
 }
 
-struct conn_timeout {
-	struct timer_list timer;
-	struct iscsit_conn *conn;
-};
-
-static void iscsi_target_login_timeout(struct timer_list *t)
-{
-	struct conn_timeout *timeout = from_timer(timeout, t, timer);
-	struct iscsit_conn *conn = timeout->conn;
-
-	pr_debug("Entering iscsi_target_login_timeout >>>>>>>>>>>>>>>>>>>\n");
-
-	if (conn->login_kworker) {
-		pr_debug("Sending SIGINT to conn->login_kworker %s/%d\n",
-			 conn->login_kworker->comm, conn->login_kworker->pid);
-		send_sig(SIGINT, conn->login_kworker, 1);
-	}
-}
-
 static void iscsi_target_do_login_rx(struct work_struct *work)
 {
 	struct iscsit_conn *conn = container_of(work,
@@ -562,12 +543,15 @@ static void iscsi_target_do_login_rx(struct work_struct *work)
 	struct iscsi_np *np = login->np;
 	struct iscsi_portal_group *tpg = conn->tpg;
 	struct iscsi_tpg_np *tpg_np = conn->tpg_np;
-	struct conn_timeout timeout;
 	int rc, zero_tsih = login->zero_tsih;
 	bool state;
 
 	pr_debug("entering iscsi_target_do_login_rx, conn: %p, %s:%d\n",
 			conn, current->comm, current->pid);
+
+	spin_lock(&conn->login_worker_lock);
+	set_bit(LOGIN_FLAGS_WORKER_RUNNING, &conn->login_flags);
+	spin_unlock(&conn->login_worker_lock);
 	/*
 	 * If iscsi_target_do_login_rx() has been invoked by ->sk_data_ready()
 	 * before initial PDU processing in iscsi_target_start_negotiation()
@@ -597,19 +581,16 @@ static void iscsi_target_do_login_rx(struct work_struct *work)
 		goto err;
 	}
 
-	conn->login_kworker = current;
 	allow_signal(SIGINT);
-
-	timeout.conn = conn;
-	timer_setup_on_stack(&timeout.timer, iscsi_target_login_timeout, 0);
-	mod_timer(&timeout.timer, jiffies + TA_LOGIN_TIMEOUT * HZ);
-	pr_debug("Starting login timer for %s/%d\n", current->comm, current->pid);
+	rc = iscsit_set_login_timer_kworker(conn, current);
+	if (rc < 0) {
+		/* The login timer has already expired */
+		pr_debug("iscsi_target_do_login_rx, login failed\n");
+		goto err;
+	}
 
 	rc = conn->conn_transport->iscsit_get_login_rx(conn, login);
-	del_timer_sync(&timeout.timer);
-	destroy_timer_on_stack(&timeout.timer);
 	flush_signals(current);
-	conn->login_kworker = NULL;
 
 	if (rc < 0)
 		goto err;
@@ -646,7 +627,17 @@ static void iscsi_target_do_login_rx(struct work_struct *work)
 		if (iscsi_target_sk_check_and_clear(conn,
 						    LOGIN_FLAGS_WRITE_ACTIVE))
 			goto err;
+
+		/*
+		 * Set the login timer thread pointer to NULL to prevent the
+		 * login process from getting stuck if the initiator
+		 * stops sending data.
+		 */
+		rc = iscsit_set_login_timer_kworker(conn, NULL);
+		if (rc < 0)
+			goto err;
 	} else if (rc == 1) {
+		iscsit_stop_login_timer(conn);
 		cancel_delayed_work(&conn->login_work);
 		iscsi_target_nego_release(conn);
 		iscsi_post_login_handler(np, conn, zero_tsih);
@@ -656,6 +647,7 @@ static void iscsi_target_do_login_rx(struct work_struct *work)
 
 err:
 	iscsi_target_restore_sock_callbacks(conn);
+	iscsit_stop_login_timer(conn);
 	cancel_delayed_work(&conn->login_work);
 	iscsi_target_login_drop(conn, login);
 	iscsit_deaccess_np(np, tpg, tpg_np);
@@ -1368,14 +1360,30 @@ int iscsi_target_start_negotiation(
 	 * and perform connection cleanup now.
 	 */
 	ret = iscsi_target_do_login(conn, login);
-	if (!ret && iscsi_target_sk_check_and_clear(conn, LOGIN_FLAGS_INITIAL_PDU))
-		ret = -1;
+	if (!ret) {
+		spin_lock(&conn->login_worker_lock);
+
+		if (iscsi_target_sk_check_and_clear(conn, LOGIN_FLAGS_INITIAL_PDU))
+			ret = -1;
+		else if (!test_bit(LOGIN_FLAGS_WORKER_RUNNING, &conn->login_flags)) {
+			if (iscsit_set_login_timer_kworker(conn, NULL) < 0) {
+				/*
+				 * The timeout has expired already.
+				 * Schedule login_work to perform the cleanup.
+				 */
+				schedule_delayed_work(&conn->login_work, 0);
+			}
+		}
+
+		spin_unlock(&conn->login_worker_lock);
+	}
 
 	if (ret < 0) {
 		iscsi_target_restore_sock_callbacks(conn);
 		iscsi_remove_failed_auth_entry(conn);
 	}
 	if (ret != 0) {
+		iscsit_stop_login_timer(conn);
 		cancel_delayed_work_sync(&conn->login_work);
 		iscsi_target_nego_release(conn);
 	}

drivers/target/iscsi/iscsi_target_util.c

@@ -1040,6 +1040,57 @@ void iscsit_stop_nopin_timer(struct iscsit_conn *conn)
 	spin_unlock_bh(&conn->nopin_timer_lock);
 }
 
+void iscsit_login_timeout(struct timer_list *t)
+{
+	struct iscsit_conn *conn = from_timer(conn, t, login_timer);
+	struct iscsi_login *login = conn->login;
+
+	pr_debug("Entering iscsi_target_login_timeout >>>>>>>>>>>>>>>>>>>\n");
+
+	spin_lock_bh(&conn->login_timer_lock);
+	login->login_failed = 1;
+
+	if (conn->login_kworker) {
+		pr_debug("Sending SIGINT to conn->login_kworker %s/%d\n",
+			 conn->login_kworker->comm, conn->login_kworker->pid);
+		send_sig(SIGINT, conn->login_kworker, 1);
+	} else {
+		schedule_delayed_work(&conn->login_work, 0);
+	}
+	spin_unlock_bh(&conn->login_timer_lock);
+}
+
+void iscsit_start_login_timer(struct iscsit_conn *conn, struct task_struct *kthr)
+{
+	pr_debug("Login timer started\n");
+
+	conn->login_kworker = kthr;
+	mod_timer(&conn->login_timer, jiffies + TA_LOGIN_TIMEOUT * HZ);
+}
+
+int iscsit_set_login_timer_kworker(struct iscsit_conn *conn, struct task_struct *kthr)
+{
+	struct iscsi_login *login = conn->login;
+	int ret = 0;
+
+	spin_lock_bh(&conn->login_timer_lock);
+	if (login->login_failed) {
+		/* The timer has already expired */
+		ret = -1;
+	} else {
+		conn->login_kworker = kthr;
+	}
+	spin_unlock_bh(&conn->login_timer_lock);
+
+	return ret;
+}
+
+void iscsit_stop_login_timer(struct iscsit_conn *conn)
+{
+	pr_debug("Login timer stopped\n");
+	timer_delete_sync(&conn->login_timer);
+}
+
 int iscsit_send_tx_data(
 	struct iscsit_cmd *cmd,
 	struct iscsit_conn *conn,

drivers/target/iscsi/iscsi_target_util.h

@@ -56,6 +56,10 @@ extern void iscsit_handle_nopin_timeout(struct timer_list *t);
 extern void __iscsit_start_nopin_timer(struct iscsit_conn *);
 extern void iscsit_start_nopin_timer(struct iscsit_conn *);
 extern void iscsit_stop_nopin_timer(struct iscsit_conn *);
+extern void iscsit_login_timeout(struct timer_list *t);
+extern void iscsit_start_login_timer(struct iscsit_conn *, struct task_struct *kthr);
+extern void iscsit_stop_login_timer(struct iscsit_conn *);
+extern int iscsit_set_login_timer_kworker(struct iscsit_conn *, struct task_struct *kthr);
 extern int iscsit_send_tx_data(struct iscsit_cmd *, struct iscsit_conn *, int);
 extern int iscsit_fe_sendpage_sg(struct iscsit_cmd *, struct iscsit_conn *);
 extern int iscsit_tx_login_rsp(struct iscsit_conn *, u8, u8);

include/target/iscsi/iscsi_target_core.h

@@ -562,12 +562,14 @@ struct iscsit_conn {
 #define LOGIN_FLAGS_READ_ACTIVE		2
 #define LOGIN_FLAGS_WRITE_ACTIVE	3
 #define LOGIN_FLAGS_CLOSED		4
+#define LOGIN_FLAGS_WORKER_RUNNING	5
 	unsigned long		login_flags;
 	struct delayed_work	login_work;
 	struct iscsi_login	*login;
 	struct timer_list	nopin_timer;
 	struct timer_list	nopin_response_timer;
 	struct timer_list	transport_timer;
+	struct timer_list	login_timer;
 	struct task_struct	*login_kworker;
 	/* Spinlock used for add/deleting cmd's from conn_cmd_list */
 	spinlock_t		cmd_lock;
@@ -576,6 +578,8 @@ struct iscsit_conn {
 	spinlock_t		nopin_timer_lock;
 	spinlock_t		response_queue_lock;
 	spinlock_t		state_lock;
+	spinlock_t		login_timer_lock;
+	spinlock_t		login_worker_lock;
 	/* libcrypto RX and TX contexts for crc32c */
 	struct ahash_request	*conn_rx_hash;
 	struct ahash_request	*conn_tx_hash;
@@ -792,15 +796,13 @@ struct iscsi_np {
 	enum np_thread_state_table np_thread_state;
 	bool                    enabled;
 	atomic_t		np_reset_count;
-	enum iscsi_timer_flags_table np_login_timer_flags;
 	u32			np_exports;
 	enum np_flags_table	np_flags;
 	spinlock_t		np_thread_lock;
 	struct completion	np_restart_comp;
 	struct socket		*np_socket;
 	struct sockaddr_storage np_sockaddr;
 	struct task_struct	*np_thread;
-	struct timer_list	np_login_timer;
 	void			*np_context;
 	struct iscsit_transport *np_transport;
 	struct list_head	np_list;