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From: Christian Brauner <christian.brauner@ubuntu.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: linux-kernel@vger.kernel.org, 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: Re: [PATCH 3/3] proc: Remove the now unnecessary internal mount of proc
Date: Fri, 28 Feb 2020 21:39:15 +0100
Message-ID: <20200228203915.jelui3l5xue5utpx@wittgenstein> (raw)
In-Reply-To: <87r1yeqxbp.fsf_-_@x220.int.ebiederm.org>

On Fri, Feb 28, 2020 at 02:19:22PM -0600, Eric W. Biederman wrote:
> 
> There remains no more code in the kernel using pids_ns->proc_mnt,
> therefore remove it from the kernel.
> 
> The big benefit of this change is that one of the most error prone and
> tricky parts of the pid namespace implementation, maintaining kernel
> mounts of proc is removed.
> 
> In addition removing the unnecessary complexity of the kernel mount
> fixes a regression that caused the proc mount options to be ignored.
> Now that the initial mount of proc comes from userspace, those mount
> options are again honored.  This fixes Android's usage of the proc
> hidepid option.
> 
> Reported-by: Alistair Strachan <astrachan@google.com>
> Fixes: e94591d0d90c ("proc: Convert proc_mount to use mount_ns.")
> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
> ---
>  fs/proc/root.c                | 36 -----------------------------------

What about proc_flush_task()? Or is this on top of your other series?

>  include/linux/pid_namespace.h |  2 --
>  include/linux/proc_ns.h       |  5 -----
>  kernel/pid.c                  |  8 --------
>  kernel/pid_namespace.c        |  7 -------
>  5 files changed, 58 deletions(-)
> 
> diff --git a/fs/proc/root.c b/fs/proc/root.c
> index 608233dfd29c..2633f10446c3 100644
> --- a/fs/proc/root.c
> +++ b/fs/proc/root.c
> @@ -292,39 +292,3 @@ struct proc_dir_entry proc_root = {
>  	.subdir		= RB_ROOT,
>  	.name		= "/proc",
>  };
> -
> -int pid_ns_prepare_proc(struct pid_namespace *ns)
> -{
> -	struct proc_fs_context *ctx;
> -	struct fs_context *fc;
> -	struct vfsmount *mnt;
> -
> -	fc = fs_context_for_mount(&proc_fs_type, SB_KERNMOUNT);
> -	if (IS_ERR(fc))
> -		return PTR_ERR(fc);
> -
> -	if (fc->user_ns != ns->user_ns) {
> -		put_user_ns(fc->user_ns);
> -		fc->user_ns = get_user_ns(ns->user_ns);
> -	}
> -
> -	ctx = fc->fs_private;
> -	if (ctx->pid_ns != ns) {
> -		put_pid_ns(ctx->pid_ns);
> -		get_pid_ns(ns);
> -		ctx->pid_ns = ns;
> -	}
> -
> -	mnt = fc_mount(fc);
> -	put_fs_context(fc);
> -	if (IS_ERR(mnt))
> -		return PTR_ERR(mnt);
> -
> -	ns->proc_mnt = mnt;
> -	return 0;
> -}
> -
> -void pid_ns_release_proc(struct pid_namespace *ns)
> -{
> -	kern_unmount(ns->proc_mnt);
> -}
> diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
> index 2ed6af88794b..4956e362e55e 100644
> --- a/include/linux/pid_namespace.h
> +++ b/include/linux/pid_namespace.h
> @@ -33,7 +33,6 @@ struct pid_namespace {
>  	unsigned int level;
>  	struct pid_namespace *parent;
>  #ifdef CONFIG_PROC_FS
> -	struct vfsmount *proc_mnt;
>  	struct dentry *proc_self;
>  	struct dentry *proc_thread_self;
>  #endif
> @@ -42,7 +41,6 @@ struct pid_namespace {
>  #endif
>  	struct user_namespace *user_ns;
>  	struct ucounts *ucounts;
> -	struct work_struct proc_work;
>  	kgid_t pid_gid;
>  	int hide_pid;
>  	int reboot;	/* group exit code if this pidns was rebooted */
> diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
> index 4626b1ac3b6c..e1106a077c1a 100644
> --- a/include/linux/proc_ns.h
> +++ b/include/linux/proc_ns.h
> @@ -50,16 +50,11 @@ enum {
>  
>  #ifdef CONFIG_PROC_FS
>  
> -extern int pid_ns_prepare_proc(struct pid_namespace *ns);
> -extern void pid_ns_release_proc(struct pid_namespace *ns);
>  extern int proc_alloc_inum(unsigned int *pino);
>  extern void proc_free_inum(unsigned int inum);
>  
>  #else /* CONFIG_PROC_FS */
>  
> -static inline int pid_ns_prepare_proc(struct pid_namespace *ns) { return 0; }
> -static inline void pid_ns_release_proc(struct pid_namespace *ns) {}
> -
>  static inline int proc_alloc_inum(unsigned int *inum)
>  {
>  	*inum = 1;
> diff --git a/kernel/pid.c b/kernel/pid.c
> index ca08d6a3aa77..60820e72634c 100644
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -144,9 +144,6 @@ void free_pid(struct pid *pid)
>  			/* Handle a fork failure of the first process */
>  			WARN_ON(ns->child_reaper);
>  			ns->pid_allocated = 0;
> -			/* fall through */
> -		case 0:
> -			schedule_work(&ns->proc_work);
>  			break;
>  		}
>  
> @@ -247,11 +244,6 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
>  		tmp = tmp->parent;
>  	}
>  
> -	if (unlikely(is_child_reaper(pid))) {
> -		if (pid_ns_prepare_proc(ns))
> -			goto out_free;
> -	}
> -
>  	get_pid_ns(ns);
>  	refcount_set(&pid->count, 1);
>  	for (type = 0; type < PIDTYPE_MAX; ++type)
> diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
> index d40017e79ebe..318fcc6ba301 100644
> --- a/kernel/pid_namespace.c
> +++ b/kernel/pid_namespace.c
> @@ -57,12 +57,6 @@ static struct kmem_cache *create_pid_cachep(unsigned int level)
>  	return READ_ONCE(*pkc);
>  }
>  
> -static void proc_cleanup_work(struct work_struct *work)

There's a comment in kernel/pid_namespace.c that references
proc_cleanup_work(). Can you please remove that as well?

> -{
> -	struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work);
> -	pid_ns_release_proc(ns);
> -}
> -
>  static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
>  {
>  	return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
> @@ -114,7 +108,6 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
>  	ns->user_ns = get_user_ns(user_ns);
>  	ns->ucounts = ucounts;
>  	ns->pid_allocated = PIDNS_ADDING;
> -	INIT_WORK(&ns->proc_work, proc_cleanup_work);
>  
>  	return ns;
>  
> -- 
> 2.25.0
> 

  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                                   ` [PATCH 0/3] proc: Actually honor the mount options Eric W. Biederman
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 [this message]
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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