ksmbd: limits exceeding the maximum allowable outstanding requests

If the client ignores the CreditResponse received from the server and
continues to send the request, ksmbd limits the requests if it exceeds
smb2 max credits.
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/connection.c

@@ -62,6 +62,7 @@ struct ksmbd_conn *ksmbd_conn_alloc(void)
 	atomic_set(&conn->req_running, 0);
 	atomic_set(&conn->r_count, 0);
 	conn->total_credits = 1;
+	conn->outstanding_credits = 1;
 
 	init_waitqueue_head(&conn->req_running_q);
 	INIT_LIST_HEAD(&conn->conns_list);

fs/ksmbd/connection.h

@@ -61,7 +61,8 @@ struct ksmbd_conn {
 	atomic_t			req_running;
 	/* References which are made for this Server object*/
 	atomic_t			r_count;
-	unsigned short			total_credits;
+	unsigned int			total_credits;
+	unsigned int			outstanding_credits;
 	spinlock_t			credits_lock;
 	wait_queue_head_t		req_running_q;
 	/* Lock to protect requests list*/

fs/ksmbd/smb2misc.c

@@ -337,7 +337,16 @@ static int smb2_validate_credit_charge(struct ksmbd_conn *conn,
 			    credit_charge, conn->total_credits);
 		ret = 1;
 	}
+
+	if ((u64)conn->outstanding_credits + credit_charge > conn->vals->max_credits) {
+		ksmbd_debug(SMB, "Limits exceeding the maximum allowable outstanding requests, given : %u, pending : %u\n",
+			    credit_charge, conn->outstanding_credits);
+		ret = 1;
+	} else
+		conn->outstanding_credits += credit_charge;
+
 	spin_unlock(&conn->credits_lock);
+
 	return ret;
 }
 

fs/ksmbd/smb2pdu.c

@@ -322,6 +322,7 @@ int smb2_set_rsp_credits(struct ksmbd_work *work)
 	}
 
 	conn->total_credits -= credit_charge;
+	conn->outstanding_credits -= credit_charge;
 	credits_requested = max_t(unsigned short,
 				  le16_to_cpu(req_hdr->CreditRequest), 1);