From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753411Ab2IFGby (ORCPT ); Thu, 6 Sep 2012 02:31:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43792 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751325Ab2IFGbw (ORCPT ); Thu, 6 Sep 2012 02:31:52 -0400 Message-ID: <50484345.8040508@redhat.com> Date: Thu, 06 Sep 2012 08:31:33 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 MIME-Version: 1.0 To: Ric Wheeler CC: axboe@kernel.dk, Mike Snitzer , Alan Cox , "Martin K. Petersen" , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Subject: Re: [Ping^3] Re: [PATCH] sg_io: allow UNMAP and WRITE SAME without CAP_SYS_RAWIO References: <1342801801-15617-1-git-send-email-pbonzini@redhat.com> <50195108.1090105@redhat.com> <503CA5BA.2040003@redhat.com> <50476480.9010302@redhat.com> <5047B38D.9000607@gmail.com> In-Reply-To: <5047B38D.9000607@gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 05/09/2012 22:18, Ric Wheeler ha scritto: >> > > Hi Paolo, > > Both of these commands are destructive. WRITE_SAME (if done without the > discard bits set) can also take a very long time to be destructive and > tie up the storage. FORMAT_UNIT has the same characteristics and yet it is allowed (btw, I don't think WRITE SAME slowness is limited to the case where a real write is requested; discarding can be just as slow). Also, the two new commands are anyway restricted to programs that have write access to the disk. If you have read-only access, you won't be able to issue any destructive command (there is one exception, START STOP UNIT is allowed even with read-only capability and is somewhat destructive). Honestly, the only reason why these two commands weren't included, is that the current whitelist is heavily tailored towards CD/DVD burning. > I think that restricting them to CAP_SYS_RAWIO seems reasonable - better > to vet and give the appropriate apps the needed capability than to > widely open up the safety check? CAP_SYS_RAWIO is so wide in its scope, that anything that requires it is insecure. Paolo