ksmbd: fix multichannel connection failure

[ Upstream commit c1883049aa9b2b7dffd3a68c5fc67fa92c174bd9 ]

ksmbd check that the session of second channel is in the session list of
first connection. If it is in session list, multichannel connection
should not be allowed.

Fixes: b95629435b84 ("ksmbd: fix racy issue from session lookup and expire")
Reported-by: Sean Heelan <seanheelan@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

fs/smb/server/mgmt/user_session.c

@@ -256,6 +256,22 @@ void ksmbd_sessions_deregister(struct ksmbd_conn *conn)
 	up_write(&sessions_table_lock);
 }
 
+bool is_ksmbd_session_in_connection(struct ksmbd_conn *conn,
+				   unsigned long long id)
+{
+	struct ksmbd_session *sess;
+
+	down_read(&conn->session_lock);
+	sess = xa_load(&conn->sessions, id);
+	if (sess) {
+		up_read(&conn->session_lock);
+		return true;
+	}
+	up_read(&conn->session_lock);
+
+	return false;
+}
+
 struct ksmbd_session *ksmbd_session_lookup(struct ksmbd_conn *conn,
 					   unsigned long long id)
 {

fs/smb/server/mgmt/user_session.h

@@ -87,6 +87,8 @@ void ksmbd_session_destroy(struct ksmbd_session *sess);
 struct ksmbd_session *ksmbd_session_lookup_slowpath(unsigned long long id);
 struct ksmbd_session *ksmbd_session_lookup(struct ksmbd_conn *conn,
 					   unsigned long long id);
+bool is_ksmbd_session_in_connection(struct ksmbd_conn *conn,
+				     unsigned long long id);
 int ksmbd_session_register(struct ksmbd_conn *conn,
 			   struct ksmbd_session *sess);
 void ksmbd_sessions_deregister(struct ksmbd_conn *conn);

fs/smb/server/smb2pdu.c

@@ -1704,44 +1704,38 @@ int smb2_sess_setup(struct ksmbd_work *work)
 
 		if (conn->dialect != sess->dialect) {
 			rc = -EINVAL;
-			ksmbd_user_session_put(sess);
 			goto out_err;
 		}
 
 		if (!(req->hdr.Flags & SMB2_FLAGS_SIGNED)) {
 			rc = -EINVAL;
-			ksmbd_user_session_put(sess);
 			goto out_err;
 		}
 
 		if (strncmp(conn->ClientGUID, sess->ClientGUID,
 			    SMB2_CLIENT_GUID_SIZE)) {
 			rc = -ENOENT;
-			ksmbd_user_session_put(sess);
 			goto out_err;
 		}
 
 		if (sess->state == SMB2_SESSION_IN_PROGRESS) {
 			rc = -EACCES;
-			ksmbd_user_session_put(sess);
 			goto out_err;
 		}
 
 		if (sess->state == SMB2_SESSION_EXPIRED) {
 			rc = -EFAULT;
-			ksmbd_user_session_put(sess);
 			goto out_err;
 		}
-		ksmbd_user_session_put(sess);
 
 		if (ksmbd_conn_need_reconnect(conn)) {
 			rc = -EFAULT;
+			ksmbd_user_session_put(sess);
 			sess = NULL;
 			goto out_err;
 		}
 
-		sess = ksmbd_session_lookup(conn, sess_id);
-		if (!sess) {
+		if (is_ksmbd_session_in_connection(conn, sess_id)) {
 			rc = -EACCES;
 			goto out_err;
 		}
@@ -1907,6 +1901,8 @@ out_err:
 
 			sess->last_active = jiffies;
 			sess->state = SMB2_SESSION_EXPIRED;
+			ksmbd_user_session_put(sess);
+			work->sess = NULL;
 			if (try_delay) {
 				ksmbd_conn_set_need_reconnect(conn);
 				ssleep(5);