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=-9.5 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, USER_AGENT_GIT 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 E107DC3B186 for ; Mon, 10 Feb 2020 15:06:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C07F72080C for ; Mon, 10 Feb 2020 15:06:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729310AbgBJPGV (ORCPT ); Mon, 10 Feb 2020 10:06:21 -0500 Received: from monster.unsafe.ru ([5.9.28.80]:54164 "EHLO mail.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729283AbgBJPGU (ORCPT ); Mon, 10 Feb 2020 10:06:20 -0500 Received: from comp-core-i7-2640m-0182e6.redhat.com (nat-pool-brq-t.redhat.com [213.175.37.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.unsafe.ru (Postfix) with ESMTPSA id B9BAFC61B1A; Mon, 10 Feb 2020 15:06:16 +0000 (UTC) From: Alexey Gladkov To: LKML , Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module Cc: Akinobu Mita , Alexander Viro , Alexey Dobriyan , Alexey Gladkov , 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: [PATCH v8 08/11] proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option Date: Mon, 10 Feb 2020 16:05:16 +0100 Message-Id: <20200210150519.538333-9-gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200210150519.538333-1-gladkov.alexey@gmail.com> References: <20200210150519.538333-1-gladkov.alexey@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: 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 Cc: Andy Lutomirski Signed-off-by: Djalal Harouni Signed-off-by: Alexey Gladkov --- 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 */ }; struct proc_fs_info { -- 2.24.1