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=-12.5 required=3.0 tests=BAYES_00, 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=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 97435C56202 for ; Fri, 6 Nov 2020 15:17:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 65A9722203 for ; Fri, 6 Nov 2020 15:17:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727800AbgKFPPc (ORCPT ); Fri, 6 Nov 2020 10:15:32 -0500 Received: from raptor.unsafe.ru ([5.9.43.93]:46042 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727020AbgKFPP0 (ORCPT ); Fri, 6 Nov 2020 10:15:26 -0500 Received: from comp-core-i7-2640m-0182e6.redhat.com (ip-89-103-122-167.net.upcbroadband.cz [89.103.122.167]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by raptor.unsafe.ru (Postfix) with ESMTPSA id E60C220A0C; Fri, 6 Nov 2020 15:15:23 +0000 (UTC) From: Alexey Gladkov To: LKML , Linux FS Devel , "Eric W . Biederman" Cc: Alexey Gladkov , Alexander Viro , Kees Cook Subject: [PATCH v4 3/3] proc: Disable cancellation of subset=pid option Date: Fri, 6 Nov 2020 16:15:12 +0100 Message-Id: <2ef0e59e5c51859997e990b9cfbeb28e1f1a5787.1604675649.git.gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.25.4 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Fri, 06 Nov 2020 15:15:24 +0000 (UTC) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/fs/proc/root.c b/fs/proc/root.c index 0ab90e24d9ae..d4a91f48c430 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 super_block *s, +static int proc_apply_options(struct super_block *s, struct fs_context *fc, struct user_namespace *user_ns) { @@ -159,8 +159,11 @@ static void proc_apply_options(struct super_block *s, if (ctx->mask & (1 << Opt_subset)) { if (ctx->pidonly == PROC_PIDONLY_ON) s->s_iflags |= SB_I_DYNAMIC; + else if (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) @@ -187,7 +190,10 @@ 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(s, fc, current_user_ns()); + ret = proc_apply_options(s, fc, current_user_ns()); + if (ret) { + return ret; + } /* * procfs isn't actually a stacking filesystem; however, there is @@ -229,8 +235,7 @@ 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(sb, fc, current_user_ns()); - return 0; + return proc_apply_options(sb, fc, current_user_ns()); } static int proc_get_tree(struct fs_context *fc) -- 2.25.4