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=-2.3 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 0E9C7C6786F for ; Thu, 1 Nov 2018 13:40:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B0F3320657 for ; Thu, 1 Nov 2018 13:40:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B0F3320657 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 S1728672AbeKAWnI (ORCPT ); Thu, 1 Nov 2018 18:43:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45354 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727998AbeKAWnH (ORCPT ); Thu, 1 Nov 2018 18:43:07 -0400 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 78BE43091742; Thu, 1 Nov 2018 13:40:07 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.31]) by smtp.corp.redhat.com (Postfix) with SMTP id 5CCCB26335; Thu, 1 Nov 2018 13:40:04 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 1 Nov 2018 14:40:05 +0100 (CET) Date: Thu, 1 Nov 2018 14:40:02 +0100 From: Oleg Nesterov To: Tycho Andersen Cc: Kees Cook , Andy Lutomirski , "Eric W . Biederman" , "Serge E . Hallyn" , Christian Brauner , Tyler Hicks , Akihiro Suda , Aleksa Sarai , linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, linux-api@vger.kernel.org Subject: Re: [PATCH v8 1/2] seccomp: add a return code to trap to userspace Message-ID: <20181101134001.GA23232@redhat.com> References: <20181029224031.29809-1-tycho@tycho.ws> <20181029224031.29809-2-tycho@tycho.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181029224031.29809-2-tycho@tycho.ws> 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 [10.5.110.41]); Thu, 01 Nov 2018 13:40:08 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/29, Tycho Andersen wrote: > > +static struct file *init_listener(struct seccomp_filter *filter) > +{ > + struct file *ret = ERR_PTR(-EBUSY); > + struct seccomp_filter *cur, *last_locked = NULL; > + int filter_nesting = 0; > + > + for (cur = current->seccomp.filter; cur; cur = cur->prev) { > + mutex_lock_nested(&cur->notify_lock, filter_nesting); > + filter_nesting++; > + last_locked = cur; > + if (cur->notif) > + goto out; > + } Somehow I no longer understand why do you need to take all locks. Isn't the first filter's notify_lock enough? IOW, for (cur = current->seccomp.filter; cur; cur = cur->prev) { if (cur->notif) return ERR_PTR(-EBUSY); first = cur; } if (first) mutex_lock(&first->notify_lock); ... initialize filter->notif ... out: if (first) mutex_unlock(&first->notify_lock); return ret; Oleg.