From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758236AbbAIVXG (ORCPT ); Fri, 9 Jan 2015 16:23:06 -0500 Received: from out01.mta.xmission.com ([166.70.13.231]:48793 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758192AbbAIVXB (ORCPT ); Fri, 9 Jan 2015 16:23:01 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: Rich Felker Cc: Al Viro , David Drysdale , "Michael Kerrisk \(man-pages\)" , Andy Lutomirski , Meredydd Luff , "linux-kernel\@vger.kernel.org" , Andrew Morton , David Miller , Thomas Gleixner , Stephen Rothwell , Oleg Nesterov , Ingo Molnar , "H. Peter Anvin" , Kees Cook , Arnd Bergmann , Christoph Hellwig , X86 ML , linux-arch , Linux API , sparclinux@vger.kernel.org References: <1416830039-21952-1-git-send-email-drysdale@google.com> <1416830039-21952-6-git-send-email-drysdale@google.com> <54AFF813.7050604@gmail.com> <20150109161302.GQ4574@brightrain.aerifal.cx> <20150109204815.GR4574@brightrain.aerifal.cx> <20150109205626.GK22149@ZenIV.linux.org.uk> <20150109205926.GT4574@brightrain.aerifal.cx> Date: Fri, 09 Jan 2015 15:20:04 -0600 In-Reply-To: <20150109205926.GT4574@brightrain.aerifal.cx> (Rich Felker's message of "Fri, 9 Jan 2015 15:59:26 -0500") Message-ID: <877fwvy7ln.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-AID: U2FsdGVkX18HEtwMQCgo9aY5ftksieFCztab198XAWc= X-SA-Exim-Connect-IP: 97.121.85.189 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 TVD_RCVD_IP Message was received from an IP address * 0.7 XMSubLong Long Subject * 1.5 TR_Symld_Words too many words that have symbols inside * 3.0 XMDrug1234561 Drug references * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.5000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa05 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_02 5+ unique symbols in subject * 0.0 T_TooManySym_04 7+ unique symbols in subject * 0.0 T_TooManySym_03 6+ unique symbols in subject * 0.0 T_TooManySym_01 4+ unique symbols in subject * 0.5 XM_Body_Dirty_Words Contains a dirty word X-Spam-DCC: XMission; sa05 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: *****;Rich Felker X-Spam-Relay-Country: X-Spam-Timing: total 265 ms - load_scoreonly_sql: 0.06 (0.0%), signal_user_changed: 3.1 (1.2%), b_tie_ro: 2.2 (0.8%), parse: 0.75 (0.3%), extract_message_metadata: 15 (5.7%), get_uri_detail_list: 1.10 (0.4%), tests_pri_-1000: 6 (2.1%), tests_pri_-950: 1.07 (0.4%), tests_pri_-900: 0.90 (0.3%), tests_pri_-400: 28 (10.7%), check_bayes: 27 (10.2%), b_tokenize: 11 (4.2%), b_tok_get_all: 8 (3.0%), b_comp_prob: 3.1 (1.2%), b_tok_touch_all: 2.4 (0.9%), b_finish: 0.67 (0.3%), tests_pri_0: 202 (76.0%), tests_pri_500: 6 (2.2%), rewrite_mail: 0.00 (0.0%) Subject: Re: [PATCHv10 man-pages 5/5] execveat.2: initial man page for execveat(2) X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Wed, 24 Sep 2014 11:00:52 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Rich Felker writes: > On Fri, Jan 09, 2015 at 08:56:26PM +0000, Al Viro wrote: >> On Fri, Jan 09, 2015 at 03:48:15PM -0500, Rich Felker wrote: >> > I think this is a case that needs to be fixed, though it's hard. The >> > normal correct usage for fexecve is to always pass an O_CLOEXEC file >> > descriptor, and the caller can't really be expected to know whether >> > the file is a script or not. We discussed workarounds before and one >> > idea I proposed was having fexecve provide a "one open only" magic >> > symlink in /proc/self/ to pass to the interpreter. It would behave >> > like an O_PATH file descriptor magic symlink in /proc/self/fd, but >> > would automatically cease to exist on the first open (at which point >> > the interpreter would have a real O_RDONLY file descriptor for the >> > underlying file). >> >> For fsck sake, folks, if you have bloody /proc, you don't need that shite >> at all! Just do execve on /proc/self/fd/n, and be done with that. >> >> The sole excuse for merging that thing in the first place had been >> "would anybody think of children^Wsclerotic^Whardened environments >> where they have no /proc at all". > > That doesn't work. With O_CLOEXEC, /proc/self/fd/n is already gone at > the time the interpreter runs, whether you're using fexecveat or > execve with "/proc/self/fd/n" to implement POSIX fexecve(). That's the > problem. This breaks the intended idiom for fexecve. O_CLOEXEC with a #! intepreter can not work. If the file descriptor is closed a #! interpreter can not open it. So I don't know why or how you want that to work but it is nonsense. This certainly does not break the intended usage for execveat. Eric