From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757207AbcASDHH (ORCPT ); Mon, 18 Jan 2016 22:07:07 -0500 Received: from mail-ig0-f193.google.com ([209.85.213.193]:33458 "EHLO mail-ig0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756882AbcASDHF (ORCPT ); Mon, 18 Jan 2016 22:07:05 -0500 MIME-Version: 1.0 In-Reply-To: <5696E366.2080605@codeaurora.org> References: <565394BE.4040506@codeaurora.org> <5696E366.2080605@codeaurora.org> Date: Tue, 19 Jan 2016 04:07:03 +0100 Message-ID: Subject: Re: [PATCH] fuse: Add support for fuse stacked I/O From: Jann Horn To: Nikhilesh Reddy Cc: Miklos Szeredi , fuse-devel , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, gregkh@linuxfoundation.org, torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, Richard Weinberger , "Theodore Ts'o" , jack@suse.cz, Antonio SJ Musumeci , sven.utcke@gmx.de, Nikolaus Rath Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2016-01-14 0:53 GMT+01:00 Nikhilesh Reddy : > Add support for filesystem stacked read/write of files > when enabled through a userspace init option of FUSE_STACKED_IO. > > When FUSE_STACKED_IO is enabled all the reads and writes > to the fuse mount point go directly to the native filesystem > rather than through the fuse daemon. All requests that aren't > read/write still go thought the userspace code. Maybe I missed it, but how does this guard against kernel stack overflow and how does it interact with the "sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH" stacking limit that overlayfs and ecryptfs use? As far as I can tell from a quick glance, someone could just stack lots of FUSE files on top of each other and cause kernel stack overflow that way, and that's nasty.