Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755943AbZC2F4e (ORCPT ); Sun, 29 Mar 2009 01:56:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751404AbZC2F4X (ORCPT ); Sun, 29 Mar 2009 01:56:23 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:42189 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751364AbZC2F4W (ORCPT ); Sun, 29 Mar 2009 01:56:22 -0400 Date: Sun, 29 Mar 2009 06:55:13 +0100 From: Al Viro To: Oleg Nesterov Cc: Hugh Dickins , Linus Torvalds , Andrew Morton , Joe Malicki , Michael Itz , Kenneth Baker , Chris Wright , David Howells , Alexey Dobriyan , Greg Kroah-Hartman , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Q: check_unsafe_exec() races (Was: [PATCH 2/4] fix setuid sometimes doesn't) Message-ID: <20090329055513.GH28946@ZenIV.linux.org.uk> References: <20090329005343.GA12139@redhat.com> <20090329041022.GF28946@ZenIV.linux.org.uk> <20090329045206.GA15519@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090329045206.GA15519@redhat.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 841 Lines: 19 On Sun, Mar 29, 2009 at 06:52:06AM +0200, Oleg Nesterov wrote: > Let's suppose that check_unsafe_exec() does not set LSM_UNSAFE_SHARE and > drops ->siglock. After that, another sub-thread does clone(CLONE_FS) without > CLONE_THREAD. Lovely. And yes, AFAICS that's a hole. > Unless we killed other threads, I can't see how we can check ->fs is not > shared with another process, we can fool ->bprm_set_creds() anyway. We can't do that, until we are past the point of no return. Charming... In principle, we can mark these threads as "-EAGAIN on such clone()" and clean that on exec failure. -- 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/