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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 7463AC282DB for ; Mon, 21 Jan 2019 07:35:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 48B55214C6 for ; Mon, 21 Jan 2019 07:35:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728768AbfAUHfi (ORCPT ); Mon, 21 Jan 2019 02:35:38 -0500 Received: from ipmail03.adl2.internode.on.net ([150.101.137.141]:54605 "EHLO ipmail03.adl2.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728014AbfAUHfc (ORCPT ); Mon, 21 Jan 2019 02:35:32 -0500 Received: from ppp59-167-129-252.static.internode.on.net (HELO dastard) ([59.167.129.252]) by ipmail03.adl2.internode.on.net with ESMTP; 21 Jan 2019 08:47:20 +1030 Received: from dave by dastard with local (Exim 4.80) (envelope-from ) id 1glLP4-0000CM-Hg; Mon, 21 Jan 2019 09:17:18 +1100 Date: Mon, 21 Jan 2019 09:17:18 +1100 From: Dave Chinner To: Jann Horn Cc: Richard Henderson , Ivan Kokshaysky , Matt Turner , Alexander Viro , linux-fsdevel@vger.kernel.org, Arnd Bergmann , "Eric W. Biederman" , Theodore Ts'o , Andreas Dilger , linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, Pavel Machek , linux-arch@vger.kernel.org, linux-api@vger.kernel.org Subject: Re: [PATCH v4 2/3] fs: don't let getdents return bogus names Message-ID: <20190120221718.GZ4205@dastard> References: <20190118161440.220134-1-jannh@google.com> <20190118161440.220134-2-jannh@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190118161440.220134-2-jannh@google.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 18, 2019 at 05:14:39PM +0100, Jann Horn wrote: > When you e.g. run `find` on a directory for which getdents returns > "filenames" that contain slashes, `find` passes those "filenames" back to > the kernel, which then interprets them as paths. That could conceivably > cause userspace to do something bad when accessing something like an > untrusted USB stick, but I'm not aware of any specific example. > > Instead of returning bogus filenames to userspace, return -EUCLEAN. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Cc: stable@vger.kernel.org > Signed-off-by: Jann Horn > --- > I ordered this fix before the refactoring one so that it can easily be > backported. > > changed in v2: > - move bogus_dirent_name() out of the #ifdef (kbuild test robot) > changed in v3: > - change calling convention (Al Viro) > - comment fix > changed in v4: > - use EFSCORRUPTED instead of EUCLEAN (Dave Chinner) > > arch/alpha/kernel/osf_sys.c | 4 ++++ > fs/readdir.c | 35 +++++++++++++++++++++++++++++++++++ > include/linux/fs.h | 2 ++ > 3 files changed, 41 insertions(+) > > diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c > index 792586038808..db1c2144d477 100644 > --- a/arch/alpha/kernel/osf_sys.c > +++ b/arch/alpha/kernel/osf_sys.c > @@ -40,6 +40,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -117,6 +118,9 @@ osf_filldir(struct dir_context *ctx, const char *name, int namlen, > unsigned int reclen = ALIGN(NAME_OFFSET + namlen + 1, sizeof(u32)); > unsigned int d_ino; > > + buf->error = check_dirent_name(name, namlen); > + if (unlikely(buf->error)) > + return -EFSCORRUPTED; > buf->error = -EINVAL; /* only used if we fail */ > if (reclen > buf->count) > return -EINVAL; > diff --git a/fs/readdir.c b/fs/readdir.c > index 2f6a4534e0df..58088510bb9c 100644 > --- a/fs/readdir.c > +++ b/fs/readdir.c > @@ -64,6 +64,26 @@ int iterate_dir(struct file *file, struct dir_context *ctx) > } > EXPORT_SYMBOL(iterate_dir); > > +/* > + * Most filesystems don't filter out bogus directory entry names, and userspace > + * can get very confused by such names. Behave as if a filesystem error had > + * happened while reading directory entries. > + */ > +int check_dirent_name(const char *name, int namlen) > +{ > + if (namlen == 0) { > + pr_err_once("%s: filesystem returned bogus empty name\n", > + __func__); > + return -EFSCORRUPTED; > + } > + if (memchr(name, '/', namlen)) { > + pr_err_once("%s: filesystem returned bogus name '%*pEhp' (contains slash)\n", > + __func__, namlen, name); > + return -EFSCORRUPTED; > + } > + return 0; > +} > + > /* > * Traditional linux readdir() handling.. > * > @@ -98,6 +118,9 @@ static int fillonedir(struct dir_context *ctx, const char *name, int namlen, > > if (buf->result) > return -EINVAL; > + buf->result = check_dirent_name(name, namlen); > + if (unlikely(buf->result)) > + return -EFSCORRUPTED; Why bother returning an error from check_dirent_name() if you just throw it away? i.e: if (!dirent_name_valid(name, namelen)) return -EFSCORRUPTED; Cheers, Dave. -- Dave Chinner david@fromorbit.com