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=-13.7 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 260AAC43331 for ; Wed, 10 Mar 2021 18:21:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E60C465002 for ; Wed, 10 Mar 2021 18:21:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233730AbhCJSUs (ORCPT ); Wed, 10 Mar 2021 13:20:48 -0500 Received: from raptor.unsafe.ru ([5.9.43.93]:56500 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233416AbhCJSUW (ORCPT ); Wed, 10 Mar 2021 13:20:22 -0500 Received: from comp-core-i7-2640m-0182e6.redhat.com (ip-94-113-225-162.net.upcbroadband.cz [94.113.225.162]) by raptor.unsafe.ru (Postfix) with ESMTPSA id 504AF4175E; Wed, 10 Mar 2021 18:20:20 +0000 (UTC) From: Alexey Gladkov To: LKML , "Eric W . Biederman" Cc: Alexey Gladkov , Alexander Viro , Kees Cook , Linux Containers , Linux FS Devel Subject: [PATCH v5 3/5] proc: Disable cancellation of subset=pid option Date: Wed, 10 Mar 2021 19:19:58 +0100 Message-Id: X-Mailer: git-send-email 2.29.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.4 (raptor.unsafe.ru [0.0.0.0]); Wed, 10 Mar 2021 18:20:20 +0000 (UTC) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org There is no way to remount procfs mountpoint with subset=pid option without it. This is done in order not to make visible what was hidden since some checks occur during mount. This patch makes this limitation explicit and demonstrates the error. Signed-off-by: Alexey Gladkov --- fs/proc/root.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/fs/proc/root.c b/fs/proc/root.c index 6a75ac717455..0d20bb67e79a 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -145,7 +145,7 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) return 0; } -static void proc_apply_options(struct proc_fs_info *fs_info, +static int proc_apply_options(struct proc_fs_info *fs_info, struct fs_context *fc, struct user_namespace *user_ns) { @@ -155,8 +155,12 @@ static void proc_apply_options(struct proc_fs_info *fs_info, fs_info->pid_gid = make_kgid(user_ns, ctx->gid); if (ctx->mask & (1 << Opt_hidepid)) fs_info->hide_pid = ctx->hidepid; - if (ctx->mask & (1 << Opt_subset)) + if (ctx->mask & (1 << Opt_subset)) { + if (ctx->pidonly != PROC_PIDONLY_ON && fs_info->pidonly == PROC_PIDONLY_ON) + return invalf(fc, "proc: subset=pid cannot be unset\n"); fs_info->pidonly = ctx->pidonly; + } + return 0; } static int proc_fill_super(struct super_block *s, struct fs_context *fc) @@ -172,7 +176,9 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) fs_info->pid_ns = get_pid_ns(ctx->pid_ns); fs_info->mounter_cred = get_cred(fc->cred); - proc_apply_options(fs_info, fc, current_user_ns()); + ret = proc_apply_options(fs_info, fc, current_user_ns()); + if (ret) + return ret; /* User space would break if executables or devices appear on proc */ s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV; @@ -224,8 +230,7 @@ static int proc_reconfigure(struct fs_context *fc) put_cred(fs_info->mounter_cred); fs_info->mounter_cred = get_cred(fc->cred); - proc_apply_options(fs_info, fc, current_user_ns()); - return 0; + return proc_apply_options(fs_info, fc, current_user_ns()); } static int proc_get_tree(struct fs_context *fc) -- 2.29.2