Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751337AbXFCUTu (ORCPT ); Sun, 3 Jun 2007 16:19:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750827AbXFCUTn (ORCPT ); Sun, 3 Jun 2007 16:19:43 -0400 Received: from x35.xmailserver.org ([64.71.152.41]:1071 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750719AbXFCUTm (ORCPT ); Sun, 3 Jun 2007 16:19:42 -0400 X-AuthUser: davidel@xmailserver.org Date: Sun, 3 Jun 2007 13:19:39 -0700 (PDT) From: Davide Libenzi X-X-Sender: davide@alien.or.mcafeemobile.com To: Ulrich Drepper cc: Linux Kernel Mailing List , Linus Torvalds , Andrew Morton , Ingo Molnar Subject: Re: [patch 2/2] ufd v1 - use unsequential O(1) fdmap In-Reply-To: <466319DB.80800@redhat.com> Message-ID: References: <4663067C.9050002@redhat.com> <466319DB.80800@redhat.com> X-GPG-FINGRPRINT: CFAE 5BEE FD36 F65E E640 56FE 0974 BF23 270F 474E X-GPG-PUBLIC_KEY: http://www.xmailserver.org/davidel.asc MIME-Version: 1.0 Content-Type: TEXT/PLAIN; CHARSET=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1912 Lines: 50 On Sun, 3 Jun 2007, Ulrich Drepper wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Davide Libenzi wrote: > >> I agree with Ingo, no need for a second magic value. Use the same value > >> as FD_UNSEQ_ALLOC which will just mean this exact value should never be > >> used as a file descriptor. > > > > I explained this in my answer to Ingo... > > And if we have a new syscall we don't need any of that special dup2 > behavior you describe. I really don't think this should be added. dup2 > should just do what POSIX specifies, nothing more. I would even suggest > to not allow to dup2() to a descriptor > RLIMIT_NOFILE unless it is > already allocated. I.e., don't allow creating arbitrary high descriptors. > > This behavior is completely consistent with the current implementation. > No bad surprises. In fact, it eliminates parts of the ABI > incompatibility I talked about. Agreed, a new syscall looks less messy. I'll make sys_dup2() to allow installing in the non-sequential area, only if there's an fd already allocated. F_DUPFD will remain unchanged (that is, not allow non-sequential fds allocations). > > Random can be expensive. At the moment is FIFO. I'm missing though how > > this can be a security flaw, when the legacy one is exactly predictable. > > It's not an added security issue. It would mean removing a possible > security the current file descriptor allocation has. > > If randomizing each allocator is too expensive then randomize at the > very least the number of the first descriptor you give out. Can you tell me how this can be a problem, and in which way making a random thing would help? - Davide - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/