ksmbd: prevent connection release during oplock break notification

ksmbd_work could be freed when after connection release.
Increment r_count of ksmbd_conn to indicate that requests
are not finished yet and to not release the connection.

Cc: stable@vger.kernel.org
Reported-by: Norbert Szetei <norbert@doyensec.com>
Tested-by: Norbert Szetei <norbert@doyensec.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

Author: namjaejeon

connection.c

@@ -485,6 +485,26 @@ void ksmbd_conn_init_server_callbacks(struct ksmbd_conn_ops *ops)
 	default_conn_ops.terminate_fn = ops->terminate_fn;
 }
 
+void ksmbd_conn_r_count_inc(struct ksmbd_conn *conn)
+{
+	atomic_inc(&conn->r_count);
+}
+
+void ksmbd_conn_r_count_dec(struct ksmbd_conn *conn)
+{
+	/*
+	 * Checking waitqueue to dropping pending requests on
+	 * disconnection. waitqueue_active is safe because it
+	 * uses atomic operation for condition.
+	 */
+	atomic_inc(&conn->refcnt);
+	if (!atomic_dec_return(&conn->r_count) && waitqueue_active(&conn->r_count_q))
+		wake_up(&conn->r_count_q);
+
+	if (atomic_dec_and_test(&conn->refcnt))
+		kfree(conn);
+}
+
 int ksmbd_conn_transport_init(void)
 {
 	int ret;

connection.h

@@ -168,6 +168,8 @@ int ksmbd_conn_transport_init(void);
 void ksmbd_conn_transport_destroy(void);
 void ksmbd_conn_lock(struct ksmbd_conn *conn);
 void ksmbd_conn_unlock(struct ksmbd_conn *conn);
+void ksmbd_conn_r_count_inc(struct ksmbd_conn *conn);
+void ksmbd_conn_r_count_dec(struct ksmbd_conn *conn);
 
 /*
  * WARNING

oplock.c

@@ -740,8 +740,7 @@ static void __smb1_oplock_break_noti(struct work_struct *wk)
 
 	if (allocate_interim_rsp_buf(work)) {
 		pr_err("smb_allocate_rsp_buf failed! ");
-		ksmbd_free_work_struct(work);
-		return;
+		goto out;
 	}
 
 	/* Init response header */
@@ -786,7 +785,9 @@ static void __smb1_oplock_break_noti(struct work_struct *wk)
 		    req->Fid, req->OplockLevel);
 
 	ksmbd_conn_write(work);
+out:
 	ksmbd_free_work_struct(work);
+	ksmbd_conn_r_count_dec(conn);
 }
 
 /**
@@ -809,6 +810,7 @@ static int smb1_oplock_break_noti(struct oplock_info *opinfo)
 	work->conn = conn;
 
 	if (opinfo->op_state == OPLOCK_ACK_WAIT) {
+		ksmbd_conn_r_count_inc(conn);
 		INIT_WORK(&work->work, __smb1_oplock_break_noti);
 		ksmbd_queue_work(work);
 
@@ -836,6 +838,7 @@ static void __smb2_oplock_break_noti(struct work_struct *wk)
 {
 	struct smb2_oplock_break *rsp = NULL;
 	struct ksmbd_work *work = container_of(wk, struct ksmbd_work, work);
+	struct ksmbd_conn *conn = work->conn;
 	struct oplock_break_info *br_info = work->request_buf;
 	struct smb2_hdr *rsp_hdr;
 	struct ksmbd_file *fp;
@@ -891,6 +894,7 @@ static void __smb2_oplock_break_noti(struct work_struct *wk)
 
 out:
 	ksmbd_free_work_struct(work);
+	ksmbd_conn_r_count_dec(conn);
 }
 
 /**
@@ -925,6 +929,7 @@ static int smb2_oplock_break_noti(struct oplock_info *opinfo)
 	work->sess = opinfo->sess;
 
 	if (opinfo->op_state == OPLOCK_ACK_WAIT) {
+		ksmbd_conn_r_count_inc(conn);
 		INIT_WORK(&work->work, __smb2_oplock_break_noti);
 		ksmbd_queue_work(work);
 
@@ -946,6 +951,7 @@ static void __smb2_lease_break_noti(struct work_struct *wk)
 {
 	struct smb2_lease_break *rsp = NULL;
 	struct ksmbd_work *work = container_of(wk, struct ksmbd_work, work);
+	struct ksmbd_conn *conn = work->conn;
 	struct lease_break_info *br_info = work->request_buf;
 	struct smb2_hdr *rsp_hdr;
 
@@ -992,6 +998,7 @@ static void __smb2_lease_break_noti(struct work_struct *wk)
 
 out:
 	ksmbd_free_work_struct(work);
+	ksmbd_conn_r_count_dec(conn);
 }
 
 /**
@@ -1031,6 +1038,7 @@ static int smb2_lease_break_noti(struct oplock_info *opinfo)
 	work->sess = opinfo->sess;
 
 	if (opinfo->op_state == OPLOCK_ACK_WAIT) {
+		ksmbd_conn_r_count_inc(conn);
 		INIT_WORK(&work->work, __smb2_lease_break_noti);
 		ksmbd_queue_work(work);
 		wait_for_break_ack(opinfo);

server.c

@@ -270,17 +270,7 @@ static void handle_ksmbd_work(struct work_struct *wk)
 
 	ksmbd_conn_try_dequeue_request(work);
 	ksmbd_free_work_struct(work);
-	/*
-	 * Checking waitqueue to dropping pending requests on
-	 * disconnection. waitqueue_active is safe because it
-	 * uses atomic operation for condition.
-	 */
-	atomic_inc(&conn->refcnt);
-	if (!atomic_dec_return(&conn->r_count) && waitqueue_active(&conn->r_count_q))
-		wake_up(&conn->r_count_q);
-
-	if (atomic_dec_and_test(&conn->refcnt))
-		kfree(conn);
+	ksmbd_conn_r_count_dec(conn);
 }
 
 /**
@@ -310,7 +300,7 @@ static int queue_ksmbd_work(struct ksmbd_conn *conn)
 	conn->request_buf = NULL;
 
 	ksmbd_conn_enqueue_request(work);
-	atomic_inc(&conn->r_count);
+	ksmbd_conn_r_count_inc(conn);
 	/* update activity on connection */
 	conn->last_active = jiffies;
 	INIT_WORK(&work->work, handle_ksmbd_work);