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>

1 files changed, 4 insertions, 2 deletions

diff --git a/include/target/iscsi/iscsi_target_core.h b/include/target/iscsi/iscsi_target_core.h
index 229118156a1f..42f4a4c0c100 100644
--- a/include/target/iscsi/iscsi_target_core.h
+++ b/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;
@@ -792,7 +796,6 @@ 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;
@@ -800,7 +803,6 @@ struct iscsi_np {
 	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;