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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 9D257C2D0DB for ; Mon, 20 Jan 2020 13:31:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 73BFF2253D for ; Mon, 20 Jan 2020 13:31:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="K6/y0bEz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726626AbgATNbX (ORCPT ); Mon, 20 Jan 2020 08:31:23 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:29820 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726619AbgATNbX (ORCPT ); Mon, 20 Jan 2020 08:31:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579527081; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ae6sHOn1ghXeqvmZk29iuHjafGzoNs8lLIkps8wijQw=; b=K6/y0bEzItSCDtZyeNojOWMR683orfvFKYDD8p8vj/QPkOwymfV6nU0Zc7F4tGAO8ZMbkl VztMUO2EwaPcK9jczGpSLSyrZT8VNde7KLHNva1lW261UnCo+0RrNDeL+M+J7q+fK2HZpN N0RMWJqNjhXPEXac4VeR2QPqhT+LUbc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-200-g9dnvO0JPdSqAUAbzP89EA-1; Mon, 20 Jan 2020 08:31:19 -0500 X-MC-Unique: g9dnvO0JPdSqAUAbzP89EA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8B9301005513; Mon, 20 Jan 2020 13:31:18 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.70]) by smtp.corp.redhat.com (Postfix) with SMTP id B57585D9E1; Mon, 20 Jan 2020 13:31:16 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 20 Jan 2020 14:31:18 +0100 (CET) Date: Mon, 20 Jan 2020 14:31:16 +0100 From: Oleg Nesterov To: Christian Brauner Cc: linux-kernel@vger.kernel.org, Kees Cook , Jann Horn , stable@vger.kernel.org, Serge Hallyn , avagin@gmail.com, Eric Paris Subject: Re: [PATCH v4] ptrace: reintroduce usage of subjective credentials in ptrace_has_cap() Message-ID: <20200120133115.GA30403@redhat.com> References: <20200118011908.23582-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200118011908.23582-1-christian.brauner@ubuntu.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On 01/18, Christian Brauner wrote: > > --- a/kernel/ptrace.c > +++ b/kernel/ptrace.c > @@ -264,12 +264,17 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state) > return ret; > } > > -static int ptrace_has_cap(struct user_namespace *ns, unsigned int mode) > +static bool ptrace_has_cap(const struct cred *cred, struct user_namespace *ns, > + unsigned int mode) > { > + int ret; > + > if (mode & PTRACE_MODE_NOAUDIT) > - return has_ns_capability_noaudit(current, ns, CAP_SYS_PTRACE); > + ret = security_capable(cred, ns, CAP_SYS_PTRACE, CAP_OPT_NOAUDIT); > else > - return has_ns_capability(current, ns, CAP_SYS_PTRACE); > + ret = security_capable(cred, ns, CAP_SYS_PTRACE, CAP_OPT_NONE); > + > + return ret == 0; > } > > /* Returns 0 on success, -errno on denial. */ > @@ -321,7 +326,7 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode) > gid_eq(caller_gid, tcred->sgid) && > gid_eq(caller_gid, tcred->gid)) > goto ok; > - if (ptrace_has_cap(tcred->user_ns, mode)) > + if (ptrace_has_cap(cred, tcred->user_ns, mode)) > goto ok; > rcu_read_unlock(); > return -EPERM; > @@ -340,7 +345,7 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode) > mm = task->mm; > if (mm && > ((get_dumpable(mm) != SUID_DUMP_USER) && > - !ptrace_has_cap(mm->user_ns, mode))) > + !ptrace_has_cap(cred, mm->user_ns, mode))) > return -EPERM; I never understood these security checks and thus I don't understand the security impact. Say, has_capability_noaudit() in __set_oom_adj(). Isn't it equally wrong? However, the patch looks "obviously correct" to me. Reviewed-by: Oleg Nesterov