From patchwork Mon Mar 30 11:12:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 11465271 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 D59E781 for ; Mon, 30 Mar 2020 11:12:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B3F8F208E4 for ; Mon, 30 Mar 2020 11:12:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729684AbgC3LMz (ORCPT ); Mon, 30 Mar 2020 07:12:55 -0400 Received: from raptor.unsafe.ru ([5.9.43.93]:42996 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729263AbgC3LMy (ORCPT ); Mon, 30 Mar 2020 07:12:54 -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 7F525208C1; Mon, 30 Mar 2020 11:12:48 +0000 (UTC) From: Alexey Gladkov To: LKML Cc: Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module , Akinobu Mita , Alexander Viro , Alexey Dobriyan , Alexey Gladkov , Andrew Morton , Andy Lutomirski , Daniel Micay , Djalal Harouni , "Dmitry V . Levin" , "Eric W . Biederman" , Greg Kroah-Hartman , Ingo Molnar , "J . Bruce Fields" , Jeff Layton , Jonathan Corbet , Kees Cook , Linus Torvalds , Oleg Nesterov Subject: [PATCH v11 8/9] proc: use human-readable values for hidehid Date: Mon, 30 Mar 2020 13:12:35 +0200 Message-Id: <20200330111235.154182-1-gladkov.alexey@gmail.com> X-Mailer: git-send-email 2.25.2 In-Reply-To: <20200327172331.418878-9-gladkov.alexey@gmail.com> References: <20200327172331.418878-9-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, 30 Mar 2020 11:12:50 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org The hidepid parameter values are becoming more and more and it becomes difficult to remember what each new magic number means. Suggested-by: Andy Lutomirski Signed-off-by: Alexey Gladkov Reviewed-by: Kees Cook --- Documentation/filesystems/proc.txt | 52 +++++++++++++++--------------- fs/proc/inode.c | 15 ++++++++- fs/proc/root.c | 36 +++++++++++++++++++-- 3 files changed, 73 insertions(+), 30 deletions(-) diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index bd0e0ab85048..af47672cb2cb 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -2025,28 +2025,28 @@ The following mount options are supported: gid= Set the group authorized to learn processes information. subset= Show only the specified subset of procfs. -hidepid=0 means classic mode - everybody may access all /proc// directories -(default). - -hidepid=1 means users may not access any /proc// directories but their -own. Sensitive files like cmdline, sched*, status are now protected against -other users. This makes it impossible to learn whether any user runs -specific program (given the program doesn't reveal itself by its behaviour). -As an additional bonus, as /proc//cmdline is unaccessible for other users, -poorly written programs passing sensitive information via program arguments are -now protected against local eavesdroppers. - -hidepid=2 means hidepid=1 plus all /proc// will be fully invisible to other -users. It doesn't mean that it hides a fact whether a process with a specific -pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"), -but it hides process' uid and gid, which may be learned by stat()'ing -/proc// otherwise. It greatly complicates an intruder's task of gathering -information about running processes, whether some daemon runs with elevated -privileges, whether other user runs some sensitive program, whether other users -run any program at all, etc. - -hidepid=4 means that procfs should only contain /proc// directories -that the caller can ptrace. +hidepid=off or hidepid=0 means classic mode - everybody may access all +/proc// directories (default). + +hidepid=noaccess or hidepid=1 means users may not access any /proc// +directories but their own. Sensitive files like cmdline, sched*, status are now +protected against other users. This makes it impossible to learn whether any +user runs specific program (given the program doesn't reveal itself by its +behaviour). As an additional bonus, as /proc//cmdline is unaccessible for +other users, poorly written programs passing sensitive information via program +arguments are now protected against local eavesdroppers. + +hidepid=invisible or hidepid=2 means hidepid=noaccess plus all /proc// will +be fully invisible to other users. It doesn't mean that it hides a fact whether +a process with a specific pid value exists (it can be learned by other means, +e.g. by "kill -0 $PID"), but it hides process' uid and gid, which may be learned +by stat()'ing /proc// otherwise. It greatly complicates an intruder's task +of gathering information about running processes, whether some daemon runs with +elevated privileges, whether other user runs some sensitive program, whether +other users run any program at all, etc. + +hidepid=ptraceable or hidepid=4 means that procfs should only contain +/proc// directories that the caller can ptrace. gid= defines a group authorized to learn processes information otherwise prohibited by hidepid=. If you use some daemon like identd which needs to learn @@ -2093,8 +2093,8 @@ creates a new procfs instance. Mount options affect own procfs instance. It means that it became possible to have several procfs instances displaying tasks with different filtering options in one pid namespace. -# mount -o hidepid=2 -t proc proc /proc -# mount -o hidepid=1 -t proc proc /tmp/proc +# mount -o hidepid=invisible -t proc proc /proc +# mount -o hidepid=noaccess -t proc proc /tmp/proc # grep ^proc /proc/mounts -proc /proc proc rw,relatime,hidepid=2 0 0 -proc /tmp/proc proc rw,relatime,hidepid=1 0 0 +proc /proc proc rw,relatime,hidepid=invisible 0 0 +proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0 diff --git a/fs/proc/inode.c b/fs/proc/inode.c index e6577ce6027b..d38a9e592352 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -24,6 +24,7 @@ #include #include #include +#include #include @@ -165,6 +166,18 @@ void proc_invalidate_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock deactivate_super(old_sb); } +static inline const char *hidepid2str(int v) +{ + switch (v) { + case HIDEPID_OFF: return "off"; + case HIDEPID_NO_ACCESS: return "noaccess"; + case HIDEPID_INVISIBLE: return "invisible"; + case HIDEPID_NOT_PTRACEABLE: return "ptraceable"; + } + WARN_ONCE(1, "bad hide_pid value: %d\n", v); + return "unknown"; +} + static int proc_show_options(struct seq_file *seq, struct dentry *root) { struct proc_fs_info *fs_info = proc_sb_info(root->d_sb); @@ -172,7 +185,7 @@ static int proc_show_options(struct seq_file *seq, struct dentry *root) if (!gid_eq(fs_info->pid_gid, GLOBAL_ROOT_GID)) seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, fs_info->pid_gid)); if (fs_info->hide_pid != HIDEPID_OFF) - seq_printf(seq, ",hidepid=%u", fs_info->hide_pid); + seq_printf(seq, ",hidepid=%s", hidepid2str(fs_info->hide_pid)); if (fs_info->pidonly != PROC_PIDONLY_OFF) seq_printf(seq, ",subset=pid"); diff --git a/fs/proc/root.c b/fs/proc/root.c index dbcd96f07c7a..ba782d6e6197 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -45,7 +45,7 @@ enum proc_param { static const struct fs_parameter_spec proc_fs_parameters[] = { fsparam_u32("gid", Opt_gid), - fsparam_u32("hidepid", Opt_hidepid), + fsparam_string("hidepid", Opt_hidepid), fsparam_string("subset", Opt_subset), {} }; @@ -58,6 +58,35 @@ static inline int valid_hidepid(unsigned int value) value == HIDEPID_NOT_PTRACEABLE); } +static int proc_parse_hidepid_param(struct fs_context *fc, struct fs_parameter *param) +{ + struct proc_fs_context *ctx = fc->fs_private; + struct fs_parameter_spec hidepid_u32_spec = fsparam_u32("hidepid", Opt_hidepid); + struct fs_parse_result result; + int base = (unsigned long)hidepid_u32_spec.data; + + if (param->type != fs_value_is_string) + return invalf(fc, "proc: unexpected type of hidepid value\n"); + + if (!kstrtouint(param->string, base, &result.uint_32)) { + ctx->hidepid = result.uint_32; + return 0; + } + + if (!strcmp(param->string, "off")) + ctx->hidepid = HIDEPID_OFF; + else if (!strcmp(param->string, "noaccess")) + ctx->hidepid = HIDEPID_NO_ACCESS; + else if (!strcmp(param->string, "invisible")) + ctx->hidepid = HIDEPID_INVISIBLE; + else if (!strcmp(param->string, "ptraceable")) + ctx->hidepid = HIDEPID_NOT_PTRACEABLE; + else + return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string); + + return 0; +} + static int proc_parse_subset_param(struct fs_context *fc, char *value) { struct proc_fs_context *ctx = fc->fs_private; @@ -97,9 +126,10 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) break; case Opt_hidepid: - if (!valid_hidepid(result.uint_32)) + if (proc_parse_hidepid_param(fc, param)) + return -EINVAL; + if (!valid_hidepid(ctx->hidepid)) return invalf(fc, "proc: unknown value of hidepid.\n"); - ctx->hidepid = result.uint_32; break; case Opt_subset: