diff --git a/fs/fs.c b/fs/fs.c
index f63a2dd..b7e7c63 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -738,6 +738,11 @@
 	struct fs_driver_d *fsdrv;
 	int ret;
 
+	if ((f->flags & O_ACCMODE) == O_WRONLY) {
+		ret = -EBADF;
+		goto out;
+	}
+
 	fsdrv = f->fsdev->driver;
 
 	if (f->size != FILE_SIZE_STREAM && f->pos + count > f->size)
@@ -747,7 +752,7 @@
 		return 0;
 
 	ret = fsdrv->read(&f->fsdev->dev, f, buf, count);
-
+out:
 	if (ret < 0)
 		errno = -ret;
 	return ret;
@@ -796,6 +801,11 @@
 	struct fs_driver_d *fsdrv;
 	int ret;
 
+	if (!(f->flags & O_ACCMODE)) {
+		ret = -EBADF;
+		goto out;
+	}
+
 	fsdrv = f->fsdev->driver;
 	if (f->size != FILE_SIZE_STREAM && f->pos + count > f->size) {
 		ret = fsdrv->truncate(&f->fsdev->dev, f, f->pos + count);