From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40151) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dVzED-0002MH-4b for qemu-devel@nongnu.org; Fri, 14 Jul 2017 07:57:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dVzEC-0003de-Cy for qemu-devel@nongnu.org; Fri, 14 Jul 2017 07:57:49 -0400 Date: Fri, 14 Jul 2017 19:57:43 +0800 From: Fam Zheng Message-ID: <20170714115742.GG18687@lemon> References: <20170714110048.GC28095@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170714110048.GC28095@redhat.com> Subject: Re: [Qemu-devel] qcow2 not cleaning up during image create failure List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, Kevin Wolf On Fri, 07/14 12:00, Daniel P. Berrange wrote: > I've just been looking at the qcow2 image creation code, and found that > if any method in qcow2_create2() returns an error, then we'll report that, > but leave the newly created image file on disk in some partially initialized > state. A user may unwittingly use this file later with undefined behaviour. > This is particularly bad if we fail to setup encryption, because the user > is left with a file with no encryption enabled. > > So I'm wondering how is the best way to clean up after failure ? > > Naively I would like to just unlink(filename), but IIUC, filename is > not guaranteed to refer to a local file, and AFAIK, there is not > bdrv_delete() method todo this portably. > > If we can't delete a file (because its a block device or network > volume), then we must at least blank out the just-written qcow2 > header with zeros. > > Ideas / suggestions. Or just write the header as the last step? Fam