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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6417AC43441 for ; Wed, 28 Nov 2018 12:35:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2930A20989 for ; Wed, 28 Nov 2018 12:35:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2930A20989 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728092AbeK1XhY (ORCPT ); Wed, 28 Nov 2018 18:37:24 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38266 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727676AbeK1XhY (ORCPT ); Wed, 28 Nov 2018 18:37:24 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8E4FE308FF0C; Wed, 28 Nov 2018 12:35:52 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.12]) by smtp.corp.redhat.com (Postfix) with SMTP id 3A4ED2DE67; Wed, 28 Nov 2018 12:35:47 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 28 Nov 2018 13:35:52 +0100 (CET) Date: Wed, 28 Nov 2018 13:35:46 +0100 From: Oleg Nesterov To: "Dmitry V. Levin" Cc: Elvira Khabirova , Steven Rostedt , Ingo Molnar , Eugene Syromyatnikov , Andy Lutomirski , strace-devel@lists.strace.io, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH RESEND v3 3/3] ptrace: add PTRACE_EVENT_SECCOMP support to PTRACE_GET_SYSCALL_INFO Message-ID: <20181128123545.GA30395@redhat.com> References: <20181125022150.46258a20@akathisia> <20181125022340.5703400f@akathisia> <20181126143524.GB1660@redhat.com> <20181127040732.1c9f7965@akathisia> <20181127123116.GA13284@redhat.com> <20181127232753.GA18755@altlinux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181127232753.GA18755@altlinux.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Wed, 28 Nov 2018 12:35:52 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/28, Dmitry V. Levin wrote: > > > Just like ptrace_request(PTRACE_LISTEN) > > does but you can do this lockless (no need to lock_task_sighand()). > > Why this can be done lockless? All other places in that file do > the locking, PTRACE_LISTEN too doesn't need lock_task_sighand() to access ->last_siginfo, this code predates ptrace_freeze_traced() which ensures that the tracee can't go away and clear ->last_siginfo. However, unlike ptrace_get_syscall(), PTRACE_LISTEN needs spin_lock_irq(siglock), it modifies ->jobctl and calls signal_wake_up(). > > Of course, debugger can do PTRACE_SETSIGINFO and confuse itself but probably we > > do not care? > > The only potential issue I could think of is whether PTRACE_SETSIGINFO > could be used this way to cause an information leak by making > PTRACE_GET_SYSCALL_INFO access some unrelated data. Well, afaics ptrace_get_syscall() does nothing "special", debugger can use other PTRACE_ requests to get the same info? Oleg.