From patchwork Fri Jul 16 10:46:01 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 12381959 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=-19.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 6DD30C07E95 for ; Fri, 16 Jul 2021 10:46:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 572E961402 for ; Fri, 16 Jul 2021 10:46:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239623AbhGPKtp (ORCPT ); Fri, 16 Jul 2021 06:49:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:52156 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239590AbhGPKtn (ORCPT ); Fri, 16 Jul 2021 06:49:43 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A905C613FC; Fri, 16 Jul 2021 10:46:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1626432408; bh=ZzDOAMdJ5lHEY2dNQ7o9jwZutsDPDTAfabK8gQhelcU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nUfa6wUxAUiRHaA4WyND6EKFUJUT8B9lDerSNVKcnolQqobsI22sEe7K9XUS1Lh2u +YQfhx/891tlBghE7tGhNMfkI4VPPcwuE34IhPkcVKYETQQ9VNp71rc1US9+mPJDWU vvnJgMIGy+XxmcWOH7DqT4rBtorcUdFIaNUOrOuGEGbnua4ae8jOcOvSVEGdGVhbOa P8YmVNZKUCLs/0N5gyaF7J77GXMhyqhnkWHgmfxBeDGweL0h+K89HBtfJzNCNK8/JE 1zE2re2wCSVIAHyB02xRAs1BhLBhI8GvQ4HaWN73Nvpur1vdCyaQUO+2gFV69Df3hQ WXGC3zpT0X7Ug== From: Alexey Gladkov To: LKML , "Eric W . Biederman" Cc: Alexander Viro , Kees Cook , Linux Containers , Linux FS Devel Subject: [RESEND PATCH v6 3/5] proc: Disable cancellation of subset=pid option Date: Fri, 16 Jul 2021 12:46:01 +0200 Message-Id: <883677463902534d2de724dca9ff139f6ad777b8.1626432185.git.legion@kernel.org> X-Mailer: git-send-email 2.29.3 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org When procfs is mounted with subset=pid option, where is no way to remount it with this option removed. This is done in order not to make visible what ever was hidden since some checks occur during mount. This patch makes the limitation explicit and prints an error message. 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)