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_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 34B19C49ED6 for ; Wed, 11 Sep 2019 13:52:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 06CAC206CD for ; Wed, 11 Sep 2019 13:52:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728256AbfIKNwk (ORCPT ); Wed, 11 Sep 2019 09:52:40 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:57122 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728090AbfIKNwj (ORCPT ); Wed, 11 Sep 2019 09:52:39 -0400 Received: from [148.69.85.38] (helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1i8330-0005t7-JG; Wed, 11 Sep 2019 13:52:38 +0000 Date: Wed, 11 Sep 2019 15:52:37 +0200 From: Christian Brauner To: Andrew Morton Cc: Eugene Syromiatnikov , linux-kernel@vger.kernel.org, Oleg Nesterov , "Peter Zijlstra (Intel)" , Ingo Molnar , "Dmitry V. Levin" , Eric Biederman Subject: Re: [PATCH v2] fork: check exit_signal passed in clone3() call Message-ID: <20190911135236.73l6icwxqff7fkw5@wittgenstein> References: <20190910175852.GA15572@asgard.redhat.com> <20190911064852.9f236d4c201b50e14d717c14@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190911064852.9f236d4c201b50e14d717c14@linux-foundation.org> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 11, 2019 at 06:48:52AM -0700, Andrew Morton wrote: > On Tue, 10 Sep 2019 18:58:52 +0100 Eugene Syromiatnikov wrote: > > > Previously, higher 32 bits of exit_signal fields were lost when > > copied to the kernel args structure (that uses int as a type for the > > respective field). Moreover, as Oleg has noted[1], exit_signal is used > > unchecked, so it has to be checked for sanity before use; for the legacy > > syscalls, applying CSIGNAL mask guarantees that it is at least non-negative; > > however, there's no such thing is done in clone3() code path, and that can > > break at least thread_group_leader. > > > > Checking user-passed exit_signal against ~CSIGNAL mask solves both > > of these problems. > > > > [1] https://lkml.org/lkml/2019/9/10/467 > > > > * kernel/fork.c (copy_clone_args_from_user): Fail with -EINVAL if > > args.exit_signal has bits set outside CSIGNAL mask. > > (_do_fork): Note that exit_signal is expected to be checked for the > > sanity by the caller. > > > > Fixes: 7f192e3cd316 ("fork: add clone3") > > What are the user-visible runtime effects of this bug? > > Relatedly, should this fix be backported into -stable kernels? If so, why? No, as I said in my other mail clone3() is not in any released kernel yet. clone3() is going to be released in v5.3. Christian