From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D02B4C433EF for ; Wed, 20 Oct 2021 17:45:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B88C9611F2 for ; Wed, 20 Oct 2021 17:45:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231344AbhJTRrz (ORCPT ); Wed, 20 Oct 2021 13:47:55 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:40680 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231341AbhJTRrf (ORCPT ); Wed, 20 Oct 2021 13:47:35 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]:55456) by out02.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1mdFeS-00GD3B-6r; Wed, 20 Oct 2021 11:45:20 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95]:47894 helo=localhost.localdomain) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1mdFeQ-001NdN-NK; Wed, 20 Oct 2021 11:45:19 -0600 From: "Eric W. Biederman" To: linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, Linus Torvalds , Oleg Nesterov , Al Viro , Kees Cook , "Eric W. Biederman" , Gabriel Krisman Bertazi , Thomas Gleixner , Peter Zijlstra , Andy Lutomirski Date: Wed, 20 Oct 2021 12:44:00 -0500 Message-Id: <20211020174406.17889-14-ebiederm@xmission.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <87y26nmwkb.fsf@disp2133> References: <87y26nmwkb.fsf@disp2133> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-XM-SPF: eid=1mdFeQ-001NdN-NK;;;mid=<20211020174406.17889-14-ebiederm@xmission.com>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX19L3CN+Bm0VN8CY3eg1B9cZck2JU8CWhww= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH 14/20] exit/syscall_user_dispatch: Send ordinary signals on failure X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Use force_fatal_sig instead of calling do_exit directly. This ensures the ordinary signal handling path gets invoked, core dumps as appropriate get created, and for multi-threaded processes all of the threads are terminated not just a single thread. When asked Gabriel Krisman Bertazi said [1]: > ebiederm@xmission.com (Eric W. Biederman) asked: > > > Why does do_syscal_user_dispatch call do_exit(SIGSEGV) and > > do_exit(SIGSYS) instead of force_sig(SIGSEGV) and force_sig(SIGSYS)? > > > > Looking at the code these cases are not expected to happen, so I would > > be surprised if userspace depends on any particular behaviour on the > > failure path so I think we can change this. > > Hi Eric, > > There is not really a good reason, and the use case that originated the > feature doesn't rely on it. > > Unless I'm missing yet another problem and others correct me, I think > it makes sense to change it as you described. > > > Is using do_exit in this way something you copied from seccomp? > > I'm not sure, its been a while, but I think it might be just that. The > first prototype of SUD was implemented as a seccomp mode. If at some point it becomes interesting we could relax "force_fatal_sig(SIGSEGV)" to instead say "force_sig_fault(SIGSEGV, SEGV_MAPERR, sd->selector)". I avoid doing that in this patch to avoid making it possible to catch currently uncatchable signals. Cc: Gabriel Krisman Bertazi Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Andy Lutomirski [1] https://lkml.kernel.org/r/87mtr6gdvi.fsf@collabora.com Signed-off-by: "Eric W. Biederman" --- kernel/entry/syscall_user_dispatch.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c index c240302f56e2..4508201847d2 100644 --- a/kernel/entry/syscall_user_dispatch.c +++ b/kernel/entry/syscall_user_dispatch.c @@ -47,14 +47,18 @@ bool syscall_user_dispatch(struct pt_regs *regs) * access_ok() is performed once, at prctl time, when * the selector is loaded by userspace. */ - if (unlikely(__get_user(state, sd->selector))) - do_exit(SIGSEGV); + if (unlikely(__get_user(state, sd->selector))) { + force_fatal_sig(SIGSEGV); + return true; + } if (likely(state == SYSCALL_DISPATCH_FILTER_ALLOW)) return false; - if (state != SYSCALL_DISPATCH_FILTER_BLOCK) - do_exit(SIGSYS); + if (state != SYSCALL_DISPATCH_FILTER_BLOCK) { + force_fatal_sig(SIGSYS); + return true; + } } sd->on_dispatch = true; -- 2.20.1