From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751845AbeB0CUQ (ORCPT ); Mon, 26 Feb 2018 21:20:16 -0500 Received: from out03.mta.xmission.com ([166.70.13.233]:51403 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751591AbeB0CUO (ORCPT ); Mon, 26 Feb 2018 21:20:14 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: Helge Deller Cc: linux-parisc@vger.kernel.org, James Bottomley , John David Anglin , linux-kernel@vger.kernel.org, Al Viro , Oleg Nesterov , linux-arch@vger.kernel.org References: <87373b6ghs.fsf@xmission.com> <20180112005940.23279-4-ebiederm@xmission.com> <20180112222944.GA22642@ls3530.fritz.box> <87fu5s4l4b.fsf@xmission.com> <68641c9e-99c6-34d3-83aa-1241bddef33c@gmx.de> Date: Mon, 26 Feb 2018 20:19:35 -0600 In-Reply-To: <68641c9e-99c6-34d3-83aa-1241bddef33c@gmx.de> (Helge Deller's message of "Sun, 25 Feb 2018 20:49:41 +0100") Message-ID: <87r2p7uqbs.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1eqUsA-0005BQ-JK;;;mid=<87r2p7uqbs.fsf@xmission.com>;;;hst=in01.mta.xmission.com;;;ip=174.19.85.160;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX181MjbviIBrqFbPh2c7uCFcTV5bYgFfU+Q= X-SA-Exim-Connect-IP: 174.19.85.160 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 1.5 XMNoVowels Alpha-numberic number with no vowels * 0.7 XMSubLong Long Subject * 0.0 TVD_RCVD_IP Message was received from an IP address * 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 * [sa06 1397; Body=1 Fuz1=1 Fuz2=1] * 1.0 XMSubMetaSx_00 1+ Sexy Words * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: XMission; sa06 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ***;Helge Deller X-Spam-Relay-Country: X-Spam-Timing: total 271 ms - load_scoreonly_sql: 0.04 (0.0%), signal_user_changed: 2.8 (1.0%), b_tie_ro: 1.96 (0.7%), parse: 1.08 (0.4%), extract_message_metadata: 15 (5.5%), get_uri_detail_list: 2.4 (0.9%), tests_pri_-1000: 8 (3.0%), tests_pri_-950: 1.14 (0.4%), tests_pri_-900: 0.98 (0.4%), tests_pri_-400: 24 (8.8%), check_bayes: 23 (8.5%), b_tokenize: 8 (2.8%), b_tok_get_all: 8 (3.0%), b_comp_prob: 2.5 (0.9%), b_tok_touch_all: 2.8 (1.0%), b_finish: 0.60 (0.2%), tests_pri_0: 210 (77.4%), check_dkim_signature: 0.67 (0.2%), check_dkim_adsp: 2.4 (0.9%), tests_pri_500: 6 (2.1%), rewrite_mail: 0.00 (0.0%) Subject: Re: [PATCH 04/11] signal/parisc: Document a conflict with SI_USER with SIGFPE X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -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 Helge Deller writes: > On 23.02.2018 01:15, Eric W. Biederman wrote: >> Helge Deller writes: >> >>> * Eric W. Biederman : >>>> Setting si_code to 0 results in a userspace seeing an si_code of 0. >>>> This is the same si_code as SI_USER. Posix and common sense requires >>>> that SI_USER not be a signal specific si_code. As such this use of 0 >>>> for the si_code is a pretty horribly broken ABI. >>>> >>>> Further use of si_code == 0 guaranteed that copy_siginfo_to_user saw a >>>> value of __SI_KILL and now sees a value of SIL_KILL with the result >>>> that uid and pid fields are copied and which might copying the si_addr >>>> field by accident but certainly not by design. Making this a very >>>> flakey implementation. >>>> >>>> Utilizing FPE_FIXME siginfo_layout will now return SIL_FAULT and the >>>> appropriate fields will reliably be copied. >>>> >>>> This bug is 13 years old and parsic machines are no longer being built >>>> so I don't know if it possible or worth fixing it. But it is at least >>>> worth documenting this so other architectures don't make the same >>>> mistake. >>> >>> >>> I think we should fix it, even if we now break the ABI. >>> >>> It's about a "conditional trap" which needs to be handled by userspace. >>> I doubt there is any Linux code out which is utilizing this >>> parisc-specific trap. >>> >>> I'd suggest to add a new FPE trap si_code (e.g. FPE_CONDTRAP). >>> While at it, maybe we should include the already existing FPE_MDAOVF >>> from the frv architecture, so that arch/frv/include/uapi/asm/siginfo.h >>> can go completely. >>> >>> Suggested patch is below. >>> >>> I'm willing to test the patch below on the parisc architecture for a few >>> weeks. And it will break arch/x86/kernel/signal_compat.c which needs >>> looking at then too. >> >> Have you managed to test this change? > > Sadly I haven't done any further testing yet. So at this point for purposed of testing I don't think it matters which number FPE_CONDTRAP gets as long as it is non-zero. > >> I am sitting looking at another new FPE si_code and if this has been tested >> I figure FPE_CONDTRAP should get the next available FPE si_code and the >> other change should get the one that follows. > > I'm fine either way. Do you have a git tree I can pull which includes > all your patches? I can then start testing. Everything finalized is in Linus's tree. There is a patch pending review on linux-arch that defines FPE_FLTUNK that looks to be useful on several architectures. I had probably misread our earlier exchange. I had hoped you had tested that FPE_CONDTRAP did not cause problems. If that level of testing was complete I would have given FPE_CONDTRAP the next FPE number and FPE_FLTUNK the one after. As it sounds like FPE_CONDTRAP hasn't been tested enough to know if it causes problems I will encourage the patches to be merged in the other order. Eric