From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: races in ipathfs Date: Sun, 18 Mar 2012 18:45:47 +0000 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 Return-path: Content-Disposition: inline In-Reply-To: <20120119202003.GZ23916-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mike Marciniszyn Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@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... -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html