Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754633AbeANBrW (ORCPT + 1 other); Sat, 13 Jan 2018 20:47:22 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:40400 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752103AbeANBrT (ORCPT ); Sat, 13 Jan 2018 20:47:19 -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> <878td1xyda.fsf@xmission.com> Date: Sat, 13 Jan 2018 19:46:26 -0600 In-Reply-To: <878td1xyda.fsf@xmission.com> (Eric W. Biederman's message of "Sat, 13 Jan 2018 15:06:09 -0600") Message-ID: <87inc5w6tp.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=1eaXOF-00020m-5O;;;mid=<87inc5w6tp.fsf@xmission.com>;;;hst=in02.mta.xmission.com;;;ip=97.121.73.102;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX19A4vGDsmeLq0UoOpxWrMNTpYrrmlvWEgA= X-SA-Exim-Connect-IP: 97.121.73.102 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [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 in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: ebiederm@xmission.com (Eric W. Biederman) writes: > 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. >> >> Thoughts? > > I like it. Your comments about the si_codes caused me to look into how they differ across the architectures and realize they also all need to be merged into uapi/asm-generic/siginfo.h for sanity sake. In doing so I found a couple of minor issues with my other unifications. Rebased onto my tree your patch looks like the below. If it does not cause any regressions it looks like a perfect fix. The noticable change is that the first FPE si_code available across all architectures is 14 so I have used 14 instead of 10 for FPE_CONDTRAP. Eric From: Helge Deller Date: Sat, 13 Jan 2018 19:32:43 -0600 Subject: [PATCH] signal/parisc: Add FPE_CONDTRAP for conditional trap handling Posix and common sense requires that SI_USER not be a signal specific si_code. Thus add a new FPE_CONDTRAP si_code for conditional traps. -- EWB rebased onto my tree. Signed-off-by: Helge Deller Signed-off-by: "Eric W. Biederman" --- arch/parisc/include/uapi/asm/siginfo.h | 7 ------- arch/parisc/kernel/traps.c | 7 ++++--- include/uapi/asm-generic/siginfo.h | 3 ++- 3 files changed, 6 insertions(+), 11 deletions(-) diff --git a/arch/parisc/include/uapi/asm/siginfo.h b/arch/parisc/include/uapi/asm/siginfo.h index be40331f757d..4a1062e05aaf 100644 --- a/arch/parisc/include/uapi/asm/siginfo.h +++ b/arch/parisc/include/uapi/asm/siginfo.h @@ -8,11 +8,4 @@ #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 c919e6c0a687..68e671a11987 100644 --- a/arch/parisc/kernel/traps.c +++ b/arch/parisc/kernel/traps.c @@ -627,9 +627,10 @@ void notrace handle_interruption(int code, struct pt_regs *regs) on condition */ if(user_mode(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 = FPE_FIXME; + /* Let userspace app figure it out from the insn pointed + * to by si_addr. + */ + si.si_code = FPE_CONDTRAP; si.si_addr = (void __user *) regs->iaoq[0]; force_sig_info(SIGFPE, &si, current); return; diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h index 254afc31e3be..ab4fad1a0cf0 100644 --- a/include/uapi/asm-generic/siginfo.h +++ b/include/uapi/asm-generic/siginfo.h @@ -229,7 +229,8 @@ typedef struct siginfo { # define __FPE_INVASC 12 /* invalid ASCII digit */ # define __FPE_INVDEC 13 /* invalid decimal digit */ #endif -#define NSIGFPE 13 +#define FPE_CONDTRAP 14 /* trap on condition */ +#define NSIGFPE 14 /* * SIGSEGV si_codes -- 2.14.1