linux-kernel - Re: [PATCH RFC 1/4] proc: add proc_fs

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Date:   Thu, 30 Mar 2017 12:10:44 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     Djalal Harouni <tixxdz@...il.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexey Gladkov <gladkov.alexey@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux API <linux-api@...r.kernel.org>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Oleg Nesterov <oleg@...hat.com>,
        Pavel Emelyanov <xemul@...allels.com>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Kees Cook <keescook@...omium.org>,
        Dongsu Park <dpark@...teo.net>, Ingo Molnar <mingo@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        LSM List <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH RFC 1/4] proc: add proc_fs_info struct to store proc options

On Thu, Mar 30, 2017 at 8:22 AM, Djalal Harouni <tixxdz@...il.com> wrote:
> This is a preparation patch that adds a proc_fs_info to be able to store
> different procfs options. Right now some mount options are stored inside
> the pid namespace which make multiple proc share the same mount options.
> This patch will help also to fix this.
>
> Signed-off-by: Djalal Harouni <tixxdz@...il.com>

>  static struct dentry *proc_mount(struct file_system_type *fs_type,
>         int flags, const char *dev_name, void *data)
>  {
> +       int error;
> +       struct super_block *sb;
>         struct pid_namespace *ns;
> +       struct proc_fs_info *fs_info;
> +
> +       if (!(flags & MS_KERNMOUNT) && !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
> +               return ERR_PTR(-EPERM);

Why is this check needed?

> diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
> index 2d2bf59..e1cb9c3 100644
> --- a/include/linux/proc_fs.h
> +++ b/include/linux/proc_fs.h
> @@ -6,11 +6,27 @@
>
>  #include <linux/types.h>
>  #include <linux/fs.h>
> +#include <linux/refcount.h>
> +
> +enum {
> +       PROC_FS_V1      = 1,
> +       PROC_FS_V2      = 2,
> +};
> +
> +struct proc_fs_info {
> +       refcount_t users;
> +       struct pid_namespace *pid_ns;
> +       kgid_t pid_gid;
> +       int hide_pid;
> +       int version;
> +};

What is version?

Should this patch have just users and pid_ns and move the other stuff
to patch 2?