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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 EFE9BC3A5A7 for ; Wed, 4 Sep 2019 11:07:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CEFAA2339D for ; Wed, 4 Sep 2019 11:07:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729825AbfIDLHi (ORCPT ); Wed, 4 Sep 2019 07:07:38 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:50946 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729146AbfIDLHh (ORCPT ); Wed, 4 Sep 2019 07:07:37 -0400 Received: from [213.220.153.21] (helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.76) (envelope-from ) id 1i5T8Q-0004Nc-0P; Wed, 04 Sep 2019 11:07:34 +0000 Date: Wed, 4 Sep 2019 13:07:33 +0200 From: Christian Brauner To: Greg Kroah-Hartman Cc: devel@driverdev.osuosl.org, Todd Kjos , Martijn Coenen , linux-kernel@vger.kernel.org, Joel Fernandes , Arve =?utf-8?B?SGrDuG5uZXbDpWc=?= , Hridya Valsaraju , kernel-team@android.com Subject: Re: [PATCH v3 2/2] binder: Validate the default binderfs device names. Message-ID: <20190904110732.e2ddiact3jvd73pt@wittgenstein> References: <20190808222727.132744-1-hridya@google.com> <20190808222727.132744-3-hridya@google.com> <20190809145508.GD16262@kroah.com> <20190809181439.qrs2k7l23ot4am4s@wittgenstein> <20190904071929.GA19830@kroah.com> <20190904104431.ehzyllugr6fr2vjz@wittgenstein> <20190904104939.GA20711@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190904104939.GA20711@kroah.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 04, 2019 at 12:49:39PM +0200, Greg Kroah-Hartman wrote: > On Wed, Sep 04, 2019 at 12:44:32PM +0200, Christian Brauner wrote: > > On Wed, Sep 04, 2019 at 09:19:29AM +0200, Greg Kroah-Hartman wrote: > > > On Fri, Aug 09, 2019 at 11:41:12AM -0700, Hridya Valsaraju wrote: > > > > On Fri, Aug 9, 2019 at 11:14 AM Christian Brauner > > > > wrote: > > > > > > > > > > On Fri, Aug 09, 2019 at 04:55:08PM +0200, Greg Kroah-Hartman wrote: > > > > > > On Thu, Aug 08, 2019 at 03:27:26PM -0700, Hridya Valsaraju wrote: > > > > > > > Length of a binderfs device name cannot exceed BINDERFS_MAX_NAME. > > > > > > > This patch adds a check in binderfs_init() to ensure the same > > > > > > > for the default binder devices that will be created in every > > > > > > > binderfs instance. > > > > > > > > > > > > > > Co-developed-by: Christian Brauner > > > > > > > Signed-off-by: Christian Brauner > > > > > > > Signed-off-by: Hridya Valsaraju > > > > > > > --- > > > > > > > drivers/android/binderfs.c | 12 ++++++++++++ > > > > > > > 1 file changed, 12 insertions(+) > > > > > > > > > > > > > > diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c > > > > > > > index aee46dd1be91..55c5adb87585 100644 > > > > > > > --- a/drivers/android/binderfs.c > > > > > > > +++ b/drivers/android/binderfs.c > > > > > > > @@ -570,6 +570,18 @@ static struct file_system_type binder_fs_type = { > > > > > > > int __init init_binderfs(void) > > > > > > > { > > > > > > > int ret; > > > > > > > + const char *name; > > > > > > > + size_t len; > > > > > > > + > > > > > > > + /* Verify that the default binderfs device names are valid. */ > > > > > > > > > > > > And by "valid" you only mean "not bigger than BINDERFS_MAX_NAME, right? > > > > > > > > > > > > > + name = binder_devices_param; > > > > > > > + for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) { > > > > > > > + if (len > BINDERFS_MAX_NAME) > > > > > > > + return -E2BIG; > > > > > > > + name += len; > > > > > > > + if (*name == ',') > > > > > > > + name++; > > > > > > > + } > > > > > > > > > > > > We already tokenize the binderfs device names in binder_init(), why not > > > > > > check this there instead? Parsing the same string over and over isn't > > > > > > the nicest. > > > > > > > > > > non-binderfs binder devices do not have their limit set to > > > > > BINDERFS_NAME_MAX. That's why the check has likely been made specific to > > > > > binderfs binder devices which do have that limit. > > > > > > > > > > > > Thank you Greg and Christian, for taking another look. Yes, > > > > non-binderfs binder devices not having this limitation is the reason > > > > why the check was made specific to binderfs devices. Also, when > > > > CONFIG_ANDROID_BINDERFS is set, patch 1/2 disabled the same string > > > > being parsed in binder_init(). > > > > > > > > > > > > > > But, in practice, 255 is the standard path-part limit that no-one really > > > > > exceeds especially not for stuff such as device nodes which usually have > > > > > rather standard naming schemes (e.g. binder, vndbinder, hwbinder, etc.). > > > > > So yes, we can move that check before both the binderfs binder device > > > > > and non-binderfs binder device parsing code and treat it as a generic > > > > > check. > > > > > Then we can also backport that check as you requested in the other mail. > > > > > Unless Hridya or Todd have objections, of course. > > > > > > > > I do not have any objections to adding a generic check in binder_init() instead. > > > > > > Was this patchset going to be redone based on this? > > > > No, we decided to leave this check specific to binderfs for now because > > the length limit only applies to binderfs devices. If you really want to > > have this check in binder we can send a follow-up. I would prefer to > > take the series as is. > > > > Btw, for the two binderfs series from Hridya, do you want me to get a > > branch ready and send you a PR for both of them together? > > Patches in email is fine, but can someone resend this one as I no longer > have this series in my queue anymore? Done! Christian