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=-6.5 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 CDD02C2BA83 for ; Wed, 12 Feb 2020 14:34:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A6DA1206D7 for ; Wed, 12 Feb 2020 14:34:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727526AbgBLOeI (ORCPT ); Wed, 12 Feb 2020 09:34:08 -0500 Received: from monster.unsafe.ru ([5.9.28.80]:60116 "EHLO mail.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727092AbgBLOeI (ORCPT ); Wed, 12 Feb 2020 09:34:08 -0500 Received: from comp-core-i7-2640m-0182e6 (nat-pool-brq-t.redhat.com [213.175.37.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.unsafe.ru (Postfix) with ESMTPSA id 940A0C61AB0; Wed, 12 Feb 2020 14:34:03 +0000 (UTC) Date: Wed, 12 Feb 2020 15:34:01 +0100 From: Alexey Gladkov To: Jordan Glover Cc: LKML , Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module , Akinobu Mita , Alexander Viro , Alexey Dobriyan , Andrew Morton , Andy Lutomirski , Daniel Micay , Djalal Harouni , "Dmitry V . Levin" , "Eric W . Biederman" , Greg Kroah-Hartman , Ingo Molnar , "J . Bruce Fields" , Jeff Layton , Jonathan Corbet , Kees Cook , Linus Torvalds , Oleg Nesterov , Solar Designer Subject: Re: [PATCH v8 08/11] proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option Message-ID: <20200212143401.vjiqsdmf55e7wsdc@comp-core-i7-2640m-0182e6> Mail-Followup-To: Jordan Glover , LKML , Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module , Akinobu Mita , Alexander Viro , Alexey Dobriyan , Andrew Morton , Andy Lutomirski , Daniel Micay , Djalal Harouni , "Dmitry V . Levin" , "Eric W . Biederman" , Greg Kroah-Hartman , Ingo Molnar , "J . Bruce Fields" , Jeff Layton , Jonathan Corbet , Kees Cook , Linus Torvalds , Oleg Nesterov , Solar Designer References: <20200210150519.538333-1-gladkov.alexey@gmail.com> <20200210150519.538333-9-gladkov.alexey@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Feb 10, 2020 at 04:29:31PM +0000, Jordan Glover wrote: > On Monday, February 10, 2020 3:05 PM, Alexey Gladkov wrote: > > > If "hidepid=4" mount option is set then do not instantiate pids that > > we can not ptrace. "hidepid=4" means that procfs should only contain > > pids that the caller can ptrace. > > > > Cc: Kees Cook keescook@chromium.org > > Cc: Andy Lutomirski luto@kernel.org > > Signed-off-by: Djalal Harouni tixxdz@gmail.com > > Signed-off-by: Alexey Gladkov gladkov.alexey@gmail.com > > > > fs/proc/base.c | 15 +++++++++++++++ > > fs/proc/root.c | 14 +++++++++++--- > > include/linux/proc_fs.h | 1 + > > 3 files changed, 27 insertions(+), 3 deletions(-) > > > > diff --git a/fs/proc/base.c b/fs/proc/base.c > > index 24b7c620ded3..49937d54e745 100644 > > --- a/fs/proc/base.c > > +++ b/fs/proc/base.c > > @@ -699,6 +699,14 @@ static bool has_pid_permissions(struct proc_fs_info *fs_info, > > struct task_struct *task, > > int hide_pid_min) > > { > > > > - /* > > - - If 'hidpid' mount option is set force a ptrace check, > > - - we indicate that we are using a filesystem syscall > > - - by passing PTRACE_MODE_READ_FSCREDS > > - */ > > - if (proc_fs_hide_pid(fs_info) == HIDEPID_NOT_PTRACABLE) > > - return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS); > > > > > > - if (proc_fs_hide_pid(fs_info) < hide_pid_min) > > return true; > > if (in_group_p(proc_fs_pid_gid(fs_info))) > > @@ -3271,7 +3279,14 @@ struct dentry *proc_pid_lookup(struct dentry *dentry, unsigned int flags) > > if (!task) > > goto out; > > > > - /* Limit procfs to only ptracable tasks */ > > - if (proc_fs_hide_pid(fs_info) == HIDEPID_NOT_PTRACABLE) { > > - if (!has_pid_permissions(fs_info, task, HIDEPID_NO_ACCESS)) > > > > > > - goto out_put_task; > > > > > > - } > > - result = proc_pid_instantiate(dentry, task, NULL); > > +out_put_task: > > put_task_struct(task); > > out: > > return result; > > diff --git a/fs/proc/root.c b/fs/proc/root.c > > index e2bb015da1a8..5e27bb31f125 100644 > > --- a/fs/proc/root.c > > +++ b/fs/proc/root.c > > @@ -52,6 +52,15 @@ static const struct fs_parameter_description proc_fs_parameters = { > > .specs = proc_param_specs, > > }; > > > > +static inline int > > +valid_hidepid(unsigned int value) > > +{ > > > > - return (value == HIDEPID_OFF || > > - value == HIDEPID_NO_ACCESS || > > > > > > - value == HIDEPID_INVISIBLE || > > > > > > - value == HIDEPID_NOT_PTRACABLE); > > > > > > > > +} > > + > > static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) > > { > > struct proc_fs_context *ctx = fc->fs_private; > > @@ -68,10 +77,9 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) > > break; > > > > case Opt_hidepid: > > > > - if (!valid_hidepid(result.uint_32)) > > > > > > - return invalf(fc, "proc: unknown value of hidepid.\\n"); > > ctx->hidepid = result.uint_32; > > > > > > > > - if (ctx->hidepid < HIDEPID_OFF || > > > > > > - ctx->hidepid > HIDEPID_INVISIBLE) > > > > > > - return invalf(fc, "proc: hidepid value must be between 0 and 2.\\n"); > > break; > > > > > > > > default: > > diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h > > index f307940f8311..6822548405a7 100644 > > --- a/include/linux/proc_fs.h > > +++ b/include/linux/proc_fs.h > > @@ -17,6 +17,7 @@ enum { > > HIDEPID_OFF = 0, > > HIDEPID_NO_ACCESS = 1, > > HIDEPID_INVISIBLE = 2, > > > > - HIDEPID_NOT_PTRACABLE = 4, /* Limit pids to only ptracable pids */ > > Is there a reason new option is "4" instead of "3"? The order 1..2..4 may be > confusing for people. This is just mask. For now hidepid values are mutually exclusive, but since it moved to uapi, I thought it would be good if there was an opportunity to combine values. -- Rgrds, legion