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 86045C55ABD 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 3B33E206A4 for ; Fri, 6 Nov 2020 15:17:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727822AbgKFPPd (ORCPT ); Fri, 6 Nov 2020 10:15:33 -0500 Received: from raptor.unsafe.ru ([5.9.43.93]:46024 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726812AbgKFPP0 (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 41BAB20A04; 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 1/3] proc: Relax check of mount visibility Date: Fri, 6 Nov 2020 16:15:10 +0100 Message-Id: <6ab3588965e4451cc01a80da7ae4c82f9701465d.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 15:15:23 +0000 (UTC) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Allow to mount of procfs with subset=pid option even if the entire procfs is not fully accessible to the user. Signed-off-by: Alexey Gladkov --- fs/namespace.c | 27 ++++++++++++++++----------- fs/proc/root.c | 17 ++++++++++------- include/linux/fs.h | 1 + 3 files changed, 27 insertions(+), 18 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 4a0f600a3328..ab9d607921da 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3949,18 +3949,23 @@ static bool mnt_already_visible(struct mnt_namespace *ns, ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) continue; - /* This mount is not fully visible if there are any - * locked child mounts that cover anything except for - * empty directories. + /* If this filesystem is completely dynamic, then it + * makes no sense to check for any child mounts. */ - list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { - struct inode *inode = child->mnt_mountpoint->d_inode; - /* Only worry about locked mounts */ - if (!(child->mnt.mnt_flags & MNT_LOCKED)) - continue; - /* Is the directory permanetly empty? */ - if (!is_empty_dir_inode(inode)) - goto next; + if (!(sb->s_iflags & SB_I_DYNAMIC)) { + /* This mount is not fully visible if there are any + * locked child mounts that cover anything except for + * empty directories. + */ + list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { + struct inode *inode = child->mnt_mountpoint->d_inode; + /* Only worry about locked mounts */ + if (!(child->mnt.mnt_flags & MNT_LOCKED)) + continue; + /* Is the directory permanetly empty? */ + if (!is_empty_dir_inode(inode)) + goto next; + } } /* Preserve the locked attributes */ *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \ diff --git a/fs/proc/root.c b/fs/proc/root.c index 5e444d4f9717..051ffe5e67ce 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -145,18 +145,22 @@ 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 void proc_apply_options(struct super_block *s, struct fs_context *fc, struct user_namespace *user_ns) { struct proc_fs_context *ctx = fc->fs_private; + struct proc_fs_info *fs_info = proc_sb_info(s); if (ctx->mask & (1 << Opt_gid)) 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) + s->s_iflags |= SB_I_DYNAMIC; fs_info->pidonly = ctx->pidonly; + } } static int proc_fill_super(struct super_block *s, struct fs_context *fc) @@ -170,9 +174,6 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) if (!fs_info) return -ENOMEM; - fs_info->pid_ns = get_pid_ns(ctx->pid_ns); - proc_apply_options(fs_info, fc, current_user_ns()); - /* User space would break if executables or devices appear on proc */ s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV; s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC; @@ -183,6 +184,9 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) s->s_time_gran = 1; s->s_fs_info = fs_info; + fs_info->pid_ns = get_pid_ns(ctx->pid_ns); + proc_apply_options(s, fc, current_user_ns()); + /* * procfs isn't actually a stacking filesystem; however, there is * too much magic going on inside it to permit stacking things on @@ -216,11 +220,10 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) static int proc_reconfigure(struct fs_context *fc) { struct super_block *sb = fc->root->d_sb; - struct proc_fs_info *fs_info = proc_sb_info(sb); sync_filesystem(sb); - proc_apply_options(fs_info, fc, current_user_ns()); + proc_apply_options(sb, fc, current_user_ns()); return 0; } diff --git a/include/linux/fs.h b/include/linux/fs.h index f5abba86107d..aff5ed9e8f82 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1413,6 +1413,7 @@ extern int send_sigurg(struct fown_struct *fown); #define SB_I_USERNS_VISIBLE 0x00000010 /* fstype already mounted */ #define SB_I_IMA_UNVERIFIABLE_SIGNATURE 0x00000020 #define SB_I_UNTRUSTED_MOUNTER 0x00000040 +#define SB_I_DYNAMIC 0x00000080 #define SB_I_SKIP_SYNC 0x00000100 /* Skip superblock at global sync */ -- 2.25.4