From patchwork Fri Jan 12 00:59:33 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 10159105 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id F082B601A1 for ; Fri, 12 Jan 2018 01:03:35 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DE038288D1 for ; Fri, 12 Jan 2018 01:03:35 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id D294C288E1; Fri, 12 Jan 2018 01:03:35 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3A7A8288D1 for ; Fri, 12 Jan 2018 01:03:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933497AbeALBBc (ORCPT ); Thu, 11 Jan 2018 20:01:32 -0500 Received: from out01.mta.xmission.com ([166.70.13.231]:35540 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933242AbeALBB2 (ORCPT ); Thu, 11 Jan 2018 20:01:28 -0500 Received: from in01.mta.xmission.com ([166.70.13.51]) by out01.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1eZnip-0003WW-9a; Thu, 11 Jan 2018 18:01:27 -0700 Received: from 97-121-73-102.omah.qwest.net ([97.121.73.102] helo=x220.int.ebiederm.org) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1eZnio-00053y-HV; Thu, 11 Jan 2018 18:01:27 -0700 From: "Eric W. Biederman" To: linux-kernel@vger.kernel.org Cc: Al Viro , Oleg Nesterov , linux-arch@vger.kernel.org, "Eric W. Biederman" , "James E.J. Bottomley" , Helge Deller , linux-parisc@vger.kernel.org Date: Thu, 11 Jan 2018 18:59:33 -0600 Message-Id: <20180112005940.23279-4-ebiederm@xmission.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <87373b6ghs.fsf@xmission.com> References: <87373b6ghs.fsf@xmission.com> X-XM-SPF: eid=1eZnio-00053y-HV; ; ; mid=<20180112005940.23279-4-ebiederm@xmission.com>; ; ; hst=in01.mta.xmission.com; ; ; ip=97.121.73.102; ; ; frm=ebiederm@xmission.com; ; ; spf=neutral X-XM-AID: U2FsdGVkX19FcL51k1qLydwcvYuOkwO1me24IIQNe1M= X-SA-Exim-Connect-IP: 97.121.73.102 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH 04/11] signal/parisc: Document a conflict with SI_USER with SIGFPE 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-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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. Possible ABI fixes includee: - Send the signal without siginfo - Don't generate a signal - Possibly assign and use an appropriate si_code - Don't handle cases which can't happen Cc: "James E.J. Bottomley" Cc: Helge Deller Cc: linux-parisc@vger.kernel.org Ref: 313c01d3e3fd ("[PATCH] PA-RISC update for 2.6.0") Histroy Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Signed-off-by: "Eric W. Biederman" --- arch/parisc/include/uapi/asm/siginfo.h | 7 +++++++ arch/parisc/kernel/traps.c | 2 +- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/parisc/include/uapi/asm/siginfo.h b/arch/parisc/include/uapi/asm/siginfo.h index 4a1062e05aaf..be40331f757d 100644 --- a/arch/parisc/include/uapi/asm/siginfo.h +++ b/arch/parisc/include/uapi/asm/siginfo.h @@ -8,4 +8,11 @@ #include +/* + * SIGFPE si_codes + */ +#ifdef __KERNEL__ +#define FPE_FIXME 0 /* Broken dup of SI_USER */ +#endif /* __KERNEL__ */ + #endif diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c index 8453724b8009..c919e6c0a687 100644 --- a/arch/parisc/kernel/traps.c +++ b/arch/parisc/kernel/traps.c @@ -629,7 +629,7 @@ void notrace handle_interruption(int code, struct pt_regs *regs) si.si_signo = SIGFPE; /* Set to zero, and let the userspace app figure it out from the insn pointed to by si_addr */ - si.si_code = 0; + si.si_code = FPE_FIXME; si.si_addr = (void __user *) regs->iaoq[0]; force_sig_info(SIGFPE, &si, current); return;