From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754718Ab2CRSpt (ORCPT ); Sun, 18 Mar 2012 14:45:49 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:43198 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751979Ab2CRSps (ORCPT ); Sun, 18 Mar 2012 14:45:48 -0400 Date: Sun, 18 Mar 2012 18:45:47 +0000 From: Al Viro To: Mike Marciniszyn Cc: linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: races in ipathfs Message-ID: <20120318184547.GA6814@ZenIV.linux.org.uk> References: <20120119202003.GZ23916@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120119202003.GZ23916@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 19, 2012 at 08:20:04PM +0000, Al Viro wrote: > Use of qib_super is seriously racy. qibfs_add() (and worse, > qibfs_remove()) can happen during qibfs_mount() and qibfs_kill_super(). [snip] FWIW, I've put a completely untested patchset into git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git qibfs It tries to avoid that kind of crap by getting rid of "populate at mount time" logics - we keep (internal) mount of that sucker for as long as there are any devices owned by ib_qib, adding them on add_device() and removing on remove_device(). The only complication is with module use counts - that fs has to be a separate module, or we'll have ib_qib impossible to rmmod, because fs keeps its module pinned and any devices held by ib_qib PCI driver will keep the fs pinned, so we never get to unregistering said PCI driver. With skeleton of qibfs (static parts only) taken to ib_qib_fs.c we avoid that problem - it is what ends up being pinned down for as long as ib_qib owns any devices, but then it's pinned down by ib_qib using exports from ib_qib_fs anyway. And once ib_qib is removed, all internal references to that vfsmount and superblock disappear as well... This stuff is completely untested; I don't have the hardware in question. It does compile and survive modpost, but that's it. Please, review and comment...