From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932919AbeALBDw (ORCPT + 1 other); Thu, 11 Jan 2018 20:03:52 -0500 Received: from out03.mta.xmission.com ([166.70.13.233]:52786 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933451AbeALBBb (ORCPT ); Thu, 11 Jan 2018 20:01:31 -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 Hogan , linux-metag@vger.kernel.org Date: Thu, 11 Jan 2018 18:59:34 -0600 Message-Id: <20180112005940.23279-5-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=1eZniq-00053y-ME;;;mid=<20180112005940.23279-5-ebiederm@xmission.com>;;;hst=in01.mta.xmission.com;;;ip=97.121.73.102;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/HBhZg7Xq5kXr6SQ7Ikbx9Xj+fX64DeOQ= X-SA-Exim-Connect-IP: 97.121.73.102 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH 05/11] signal/metag: 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 hat 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. 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 Hogan Cc: linux-metag@vger.kernel.org Ref: ac919f0883e5 ("metag: Traps") Signed-off-by: "Eric W. Biederman" --- arch/metag/include/uapi/asm/siginfo.h | 7 +++++++ arch/metag/kernel/traps.c | 2 +- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/metag/include/uapi/asm/siginfo.h b/arch/metag/include/uapi/asm/siginfo.h index b54ef7186ca3..9a3f6cde9487 100644 --- a/arch/metag/include/uapi/asm/siginfo.h +++ b/arch/metag/include/uapi/asm/siginfo.h @@ -6,4 +6,11 @@ #include +/* + * SIGFPE si_codes + */ +#ifdef __KERNEL__ +#define FPE_FIXME 0 /* Broken dup of SI_USER */ +#endif /* __KERNEL__ */ + #endif diff --git a/arch/metag/kernel/traps.c b/arch/metag/kernel/traps.c index 444851e510d5..3b62b1b0c0b5 100644 --- a/arch/metag/kernel/traps.c +++ b/arch/metag/kernel/traps.c @@ -735,7 +735,7 @@ TBIRES fpe_handler(TBIRES State, int SigNum, int Triggers, int Inst, PTBI pTBI) else if (error_state & TXSTAT_FPE_INEXACT_BIT) info.si_code = FPE_FLTRES; else - info.si_code = 0; + info.si_code = FPE_FIXME; info.si_errno = 0; info.si_addr = (__force void __user *)regs->ctx.CurrPC; force_sig_info(SIGFPE, &info, current); -- 2.14.1