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From: ebiederm@xmission.com (Eric W. Biederman)
To: <linux-kernel@vger.kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>,
	Linux API <linux-api@vger.kernel.org>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	Linux Security Module <linux-security-module@vger.kernel.org>,
	Akinobu Mita <akinobu.mita@gmail.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andy Lutomirski <luto@kernel.org>,
	Daniel Micay <danielmicay@gmail.com>,
	Djalal Harouni <tixxdz@gmail.com>,
	"Dmitry V . Levin" <ldv@altlinux.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	"J . Bruce Fields" <bfields@fieldses.org>,
	Jeff Layton <jlayton@poochiereds.net>,
	Jonathan Corbet <corbet@lwn.net>,
	Kees Cook <keescook@chromium.org>,
	Oleg Nesterov <oleg@redhat.com>,
	Alexey Gladkov <gladkov.alexey@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Jeff Dike <jdike@addtoit.com>,
	Richard Weinberger <richard@nod.at>,
	Anton Ivanov <anton.ivanov@cambridgegreys.com>
Subject: [PATCH 0/3] proc: Actually honor the mount options
Date: Fri, 28 Feb 2020 14:17:41 -0600
Message-ID: <878skmsbyy.fsf_-_@x220.int.ebiederm.org> (raw)
In-Reply-To: <871rqk2brn.fsf_-_@x220.int.ebiederm.org> (Eric W. Biederman's message of "Mon, 24 Feb 2020 10:25:16 -0600")


Proc mount option handling is broken, and it has been since I
accidentally broke it in the middle 2006.

The problem is that because we perform an internal mount of proc
before user space mounts proc all of the mount options that user
specifies when mounting proc are ignored.

You can set those mount options with a remount but that is rather
surprising.

This most directly affects android which is using hidpid=2 by default.

Now that the sysctl system call support has been removed, and we have
settled on way of flushing proc dentries when a process exits without
using proc_mnt, there is an simple and easy fix.

a) Give UML mconsole it's own private mount of proc to use.
b) Stop creating the internal mount of proc

We still need Alexey Gladkov's full patch to get proc mount options to
work inside of UML, and to be generally useful.  This set of changes
is just enough to get them working as well as they have in the past.

If anyone sees any problem with this code please let me know.

Otherwise I plan to merge these set of fixes through my tree.

Link: https://lore.kernel.org/lkml/87r21tuulj.fsf@x220.int.ebiederm.org/
Link: https://lore.kernel.org/lkml/871rqk2brn.fsf_-_@x220.int.ebiederm.org/
Link: https://lore.kernel.org/lkml/20200210150519.538333-1-gladkov.alexey@gmail.com/
Link: https://lore.kernel.org/lkml/20180611195744.154962-1-astrachan@google.com/
Fixes: e94591d0d90c ("proc: Convert proc_mount to use mount_ns.")

Eric W. Biederman (3):
      uml: Don't consult current to find the proc_mnt in mconsole_proc
      uml: Create a private mount of proc for mconsole
      proc: Remove the now unnecessary internal mount of proc

 arch/um/drivers/mconsole_kern.c | 28 +++++++++++++++++++++++++++-
 fs/proc/root.c                  | 36 ------------------------------------
 include/linux/pid_namespace.h   |  2 --
 include/linux/proc_ns.h         |  5 -----
 kernel/pid.c                    |  8 --------
 kernel/pid_namespace.c          |  7 -------
 6 files changed, 27 insertions(+), 59 deletions(-)

Eric

  parent reply index

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-10 15:05 [PATCH v8 00/11] proc: modernize proc to support multiple private instances Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 01/11] proc: Rename struct proc_fs_info to proc_fs_opts Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 02/11] proc: add proc_fs_info struct to store proc information Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 03/11] proc: move /proc/{self|thread-self} dentries to proc_fs_info Alexey Gladkov
2020-02-10 18:23   ` Andy Lutomirski
2020-02-12 15:00     ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 04/11] proc: move hide_pid, pid_gid from pid_namespace " Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 05/11] proc: add helpers to set and get proc hidepid and gid mount options Alexey Gladkov
2020-02-10 18:30   ` Andy Lutomirski
2020-02-12 14:57     ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 06/11] proc: support mounting procfs instances inside same pid namespace Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 07/11] proc: flush task dcache entries from all procfs instances Alexey Gladkov
2020-02-10 17:46   ` Linus Torvalds
2020-02-10 19:23     ` Al Viro
2020-02-11  1:36   ` Eric W. Biederman
2020-02-11  4:01     ` Eric W. Biederman
2020-02-12 14:49     ` Alexey Gladkov
2020-02-12 14:59       ` Eric W. Biederman
2020-02-12 17:08         ` Alexey Gladkov
2020-02-12 18:45         ` Linus Torvalds
2020-02-12 19:16           ` Eric W. Biederman
2020-02-12 19:49             ` Linus Torvalds
2020-02-12 20:03               ` Al Viro
2020-02-12 20:35                 ` Linus Torvalds
2020-02-12 20:38                   ` Al Viro
2020-02-12 20:41                     ` Al Viro
2020-02-12 21:02                       ` Linus Torvalds
2020-02-12 21:46                         ` Eric W. Biederman
2020-02-13  0:48                           ` Linus Torvalds
2020-02-13  4:37                             ` Eric W. Biederman
2020-02-13  5:55                               ` Al Viro
2020-02-13 21:30                                 ` Linus Torvalds
2020-02-13 22:23                                   ` Al Viro
2020-02-13 22:47                                     ` Linus Torvalds
2020-02-14 14:15                                       ` Eric W. Biederman
2020-02-14  3:48                                 ` Eric W. Biederman
2020-02-20 20:46                               ` [PATCH 0/7] proc: Dentry flushing without proc_mnt Eric W. Biederman
2020-02-20 20:47                                 ` [PATCH 1/7] proc: Rename in proc_inode rename sysctl_inodes sibling_inodes Eric W. Biederman
2020-02-20 20:48                                 ` [PATCH 2/7] proc: Generalize proc_sys_prune_dcache into proc_prune_siblings_dcache Eric W. Biederman
2020-02-20 20:49                                 ` [PATCH 3/7] proc: Mov rcu_read_(lock|unlock) in proc_prune_siblings_dcache Eric W. Biederman
2020-02-20 22:33                                   ` Linus Torvalds
2020-02-20 20:49                                 ` [PATCH 4/7] proc: Use d_invalidate " Eric W. Biederman
2020-02-20 22:43                                   ` Linus Torvalds
2020-02-20 22:54                                   ` Al Viro
2020-02-20 23:00                                     ` Linus Torvalds
2020-02-20 23:03                                     ` Al Viro
2020-02-20 23:39                                       ` Eric W. Biederman
2020-02-20 20:51                                 ` [PATCH 5/7] proc: Clear the pieces of proc_inode that proc_evict_inode cares about Eric W. Biederman
2020-02-20 20:52                                 ` [PATCH 6/7] proc: Use a list of inodes to flush from proc Eric W. Biederman
2020-02-20 20:52                                 ` [PATCH 7/7] proc: Ensure we see the exit of each process tid exactly once Eric W. Biederman
2020-02-21 16:50                                   ` Oleg Nesterov
2020-02-22 15:46                                     ` Eric W. Biederman
2020-02-20 23:02                                 ` [PATCH 0/7] proc: Dentry flushing without proc_mnt Linus Torvalds
2020-02-20 23:07                                   ` Al Viro
2020-02-20 23:37                                     ` Eric W. Biederman
2020-02-24 16:25                                 ` [PATCH v2 0/6] " Eric W. Biederman
2020-02-24 16:26                                   ` [PATCH v2 1/6] proc: Rename in proc_inode rename sysctl_inodes sibling_inodes Eric W. Biederman
2020-02-24 16:27                                   ` [PATCH v2 2/6] proc: Generalize proc_sys_prune_dcache into proc_prune_siblings_dcache Eric W. Biederman
2020-02-24 16:27                                   ` [PATCH v2 3/6] proc: In proc_prune_siblings_dcache cache an aquired super block Eric W. Biederman
2020-02-24 16:28                                   ` [PATCH v2 4/6] proc: Use d_invalidate in proc_prune_siblings_dcache Eric W. Biederman
2020-02-24 16:28                                   ` [PATCH v2 5/6] proc: Clear the pieces of proc_inode that proc_evict_inode cares about Eric W. Biederman
2020-02-24 16:29                                   ` [PATCH v2 6/6] proc: Use a list of inodes to flush from proc Eric W. Biederman
2020-02-28 20:17                                   ` Eric W. Biederman [this message]
2020-02-28 20:18                                     ` [PATCH 1/3] uml: Don't consult current to find the proc_mnt in mconsole_proc Eric W. Biederman
2020-02-28 20:18                                     ` [PATCH 2/3] uml: Create a private mount of proc for mconsole Eric W. Biederman
2020-02-28 20:30                                       ` Christian Brauner
2020-02-28 21:28                                         ` Eric W. Biederman
2020-02-28 21:59                                           ` Christian Brauner
2020-02-28 20:19                                     ` [PATCH 3/3] proc: Remove the now unnecessary internal mount of proc Eric W. Biederman
2020-02-28 20:39                                       ` Christian Brauner
2020-02-28 21:40                                         ` Eric W. Biederman
2020-02-28 22:34                                     ` [PATCH 4/3] pid: Improve the comment about waiting in zap_pid_ns_processes Eric W. Biederman
2020-02-29  2:59                                       ` Christian Brauner
2020-02-14  3:49                     ` [PATCH v8 07/11] proc: flush task dcache entries from all procfs instances Eric W. Biederman
2020-02-12 19:47           ` Al Viro
2020-02-11 22:45   ` Al Viro
2020-02-12 14:26     ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 08/11] proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option Alexey Gladkov
2020-02-10 16:29   ` Jordan Glover
2020-02-12 14:34     ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 09/11] proc: add option to mount only a pids subset Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 10/11] docs: proc: add documentation for "hidepid=4" and "subset=pidfs" options and new mount behavior Alexey Gladkov
2020-02-10 18:29   ` Andy Lutomirski
2020-02-12 16:03     ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 11/11] proc: Move hidepid values to uapi as they are user interface to mount Alexey Gladkov

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