Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933665AbeALBBf (ORCPT + 1 other); Thu, 11 Jan 2018 20:01:35 -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 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-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: 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; -- 2.14.1