cifsd: fix memleak in ksmbd_vfs_stream_write()

Before assigning wbuf to stream_buf, memory allocate in
ksmbd_vfs_getcasexattr() need be freed.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifsd/vfs.c

@@ -429,6 +429,7 @@ static int ksmbd_vfs_stream_write(struct ksmbd_file *fp, char *buf, loff_t *pos,
 
 		if (v_len > 0)
 			memcpy(wbuf, stream_buf, v_len);
+		kvfree(stream_buf);
 		stream_buf = wbuf;
 	}