From patchwork Fri Jul 16 10:46:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 12381961 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 8977BC12002 for ; Fri, 16 Jul 2021 10:46:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 70D87613FE for ; Fri, 16 Jul 2021 10:46:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239653AbhGPKtq (ORCPT ); Fri, 16 Jul 2021 06:49:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:52194 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239609AbhGPKtp (ORCPT ); Fri, 16 Jul 2021 06:49:45 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 529C161400; Fri, 16 Jul 2021 10:46:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1626432410; bh=cKPUrMJlrbhdHHIfSWaYHig7589u38uBUtasPne2i+8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LWKF4NgRwNtOBvqryxN6epQsZxEV/M/nwgtM0mWh7zLfXBNQ0OirumJOHwNLIFGSx B/0K2bUdqAy7Bea4qwYP4WWRnLT2tgvBxhRI2mkG4lL/eSwOYCxGWCyP0Zg0icbVoB mMGEYzB7k1ZHYqdTHI4K9Z8CjcrbC1r3/Q7UEYQIfXmS/xFeJEjWy04kIr7umypudH 4984+UpJhKrMijSwEVIz+jLS/qEgNP+IxpcPg577A69j77zL62fXzAVdckxzxQpS06 3O4Z6UBZKYCSX/XKbtxcr1rhZLPJ5+Yw32CBmVQRzsY82zRxn2/SydRDzHFkuPB40i jyjyFhAQ4ldCQ== From: Alexey Gladkov To: LKML , "Eric W . Biederman" Cc: Alexander Viro , Kees Cook , Linux Containers , Linux FS Devel Subject: [RESEND PATCH v6 4/5] proc: Relax check of mount visibility Date: Fri, 16 Jul 2021 12:46:02 +0200 Message-Id: <88df4f859fa985b9aa3708ff859797e552dd4d33.1626432185.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 Allow to mount 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 | 30 ++++++++++++++++++------------ fs/proc/root.c | 16 ++++++++++------ include/linux/fs.h | 1 + 3 files changed, 29 insertions(+), 18 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 9d33909d0f9e..f38570fdfc3f 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3951,7 +3951,8 @@ static bool mnt_already_visible(struct mnt_namespace *ns, /* This mount is not fully visible if it's root directory * is not the root directory of the filesystem. */ - if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root) + if (!(sb->s_iflags & SB_I_DYNAMIC) && + mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root) continue; /* A local view of the mount flags */ @@ -3971,18 +3972,23 @@ 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 0d20bb67e79a..c739ed94246c 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 int proc_apply_options(struct proc_fs_info *fs_info, +static int 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->pidonly != PROC_PIDONLY_ON && fs_info->pidonly == PROC_PIDONLY_ON) + 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; } @@ -176,9 +179,6 @@ 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); - 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; @@ -190,6 +190,10 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc) s->s_time_gran = 1; s->s_fs_info = fs_info; + ret = proc_apply_options(s, fc, current_user_ns()); + if (ret) + return ret; + /* * procfs isn't actually a stacking filesystem; however, there is * too much magic going on inside it to permit stacking things on @@ -230,7 +234,7 @@ static int proc_reconfigure(struct fs_context *fc) put_cred(fs_info->mounter_cred); fs_info->mounter_cred = get_cred(fc->cred); - return proc_apply_options(fs_info, fc, current_user_ns()); + return proc_apply_options(sb, fc, current_user_ns()); } static int proc_get_tree(struct fs_context *fc) diff --git a/include/linux/fs.h b/include/linux/fs.h index fd47deea7c17..2c9a47bad796 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1390,6 +1390,7 @@ 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 */