From patchwork Mon Jul 27 14:14:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 11686959 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3A6CE138C for ; Mon, 27 Jul 2020 14:29:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2BB35208E4 for ; Mon, 27 Jul 2020 14:29:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732063AbgG0OXV (ORCPT ); Mon, 27 Jul 2020 10:23:21 -0400 Received: from raptor.unsafe.ru ([5.9.43.93]:51900 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732045AbgG0OXV (ORCPT ); Mon, 27 Jul 2020 10:23:21 -0400 Received: from comp-core-i7-2640m-0182e6.redhat.com (ip-89-102-33-211.net.upcbroadband.cz [89.102.33.211]) (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 97322209CE; Mon, 27 Jul 2020 14:15:41 +0000 (UTC) From: Alexey Gladkov To: LKML Cc: Linux FS Devel , Alexander Viro , Alexey Gladkov , "Eric W . Biederman" , Kees Cook Subject: [PATCH v1 1/2] proc: Relax check of mount visibility Date: Mon, 27 Jul 2020 16:14:10 +0200 Message-Id: <20200727141411.203770-2-gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.25.4 In-Reply-To: <20200727141411.203770-1-gladkov.alexey@gmail.com> References: <20200727141411.203770-1-gladkov.alexey@gmail.com> MIME-Version: 1.0 X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Mon, 27 Jul 2020 14:15:41 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@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 | 16 +++++++++------- include/linux/fs.h | 1 + 3 files changed, 26 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..c6bf74de1906 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -145,18 +145,21 @@ 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)) { fs_info->pidonly = ctx->pidonly; + s->s_iflags |= SB_I_DYNAMIC; + } } static int proc_fill_super(struct super_block *s, struct fs_context *fc) @@ -170,9 +173,6 @@ 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 +183,9 @@ 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 +219,10 @@ 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 */