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,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 9111DC49ED6 for ; Wed, 11 Sep 2019 14:54:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6AD0A21D79 for ; Wed, 11 Sep 2019 14:54:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728349AbfIKOyw (ORCPT ); Wed, 11 Sep 2019 10:54:52 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:60067 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727627AbfIKOyw (ORCPT ); Wed, 11 Sep 2019 10:54:52 -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 1i841A-0003CG-8l; Wed, 11 Sep 2019 14:54:48 +0000 Date: Wed, 11 Sep 2019 16:54:47 +0200 From: Christian Brauner To: Eugene Syromiatnikov Cc: Andrew Morton , 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: <20190911145446.vkcqy2shldi5ibb5@wittgenstein> References: <20190910175852.GA15572@asgard.redhat.com> <20190911064852.9f236d4c201b50e14d717c14@linux-foundation.org> <20190911135236.73l6icwxqff7fkw5@wittgenstein> <20190911141635.lafrcjwvbhjm3ezy@wittgenstein> <20190911143213.GB21600@asgard.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190911143213.GB21600@asgard.redhat.com> 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 03:32:13PM +0100, Eugene Syromiatnikov wrote: > On Wed, Sep 11, 2019 at 04:16:36PM +0200, Christian Brauner wrote: > > On Wed, Sep 11, 2019 at 03:52:36PM +0200, Christian Brauner wrote: > > > On Wed, Sep 11, 2019 at 06:48:52AM -0700, Andrew Morton wrote: > > > > What are the user-visible runtime effects of this bug? > > The userspace can set -1 as an exit_signal, and that will break process > signalling and reaping. > > > > > 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. > > > > Sigh, I spoke to soon... Hm, this is placed in _do_fork(). There's a > > chance that this might be visible in legacy clone if anyone passes in an > > invalid signal greater than NSIG right now somehow, they'd now get > > EINVAL if I'm seeing this right. > > > > So an alternative might be to only fix this in clone3() only right now > > and get this patch into 5.3 to not release clone3() with this bug from > > legacy clone duplicated. > > And we defer the actual legacy clone fix until after next merge window > > having it stew in linux-next for a couple of rcs. Distros often pull in > > rcs so if anyone notices a regression for legacy clone we'll know about > > it... valid_signal() checks at process exit time when the parent is > > supposed to be notifed will catch faulty signals anyway so it's not that > > big of a deal. > > As the patch is written, only copy_clone_args_from_user is touched (which > is used only by clone3 and not legacy clone), and the check added Great! > replicates legacy clone behaviour: userspace can set 0..CSIGNAL > as an exit_signal. Having ability to set exit_signal in NSIG..CSIGNAL Hm. The way I see it for clone3() it would make sense to only have < NSIG right away. valid_signal() won't let through anything else anyway... Since clone3() isn't out yet it doesn't make sense to replicate the (buggy) behavior of legacy clone, right? Christian