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Date: Wed, 26 Apr 2017 15:09:09 -0700
From: Andy Lutomirski <luto@...nel.org>
To: Djalal Harouni <tixxdz@...il.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Andy Lutomirski <luto@...nel.org>, 
	Kees Cook <keescook@...omium.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Linux FS Devel <linux-fsdevel@...r.kernel.org>, 
	"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, 
	LSM List <linux-security-module@...r.kernel.org>, 
	Linux API <linux-api@...r.kernel.org>, Dongsu Park <dpark@...teo.net>, 
	Casey Schaufler <casey@...aufler-ca.com>, James Morris <james.l.morris@...cle.com>, 
	"Serge E. Hallyn" <serge@...lyn.com>, Jeff Layton <jlayton@...chiereds.net>, 
	"J. Bruce Fields" <bfields@...ldses.org>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Alexey Dobriyan <adobriyan@...il.com>, Ingo Molnar <mingo@...nel.org>, 
	"Eric W. Biederman" <ebiederm@...ssion.com>, Oleg Nesterov <oleg@...hat.com>, Michal Hocko <mhocko@...e.com>, 
	Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH RFC v2 5/6] proc: instantiate only pids that we can ptrace
 on 'limit_pids=1' mount option

On Tue, Apr 25, 2017 at 5:23 AM, Djalal Harouni <tixxdz@...il.com> wrote:
> If "limit_pids=1" mount option is set then do not instantiate pids that
> we can not ptrace. "limit_pids=1" means that procfs should only contain
> pids that the caller can ptrace.
>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Andy Lutomirski <luto@...nel.org>
> Signed-off-by: Djalal Harouni <tixxdz@...il.com>
> ---
>  fs/proc/base.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 2e0f661..a663284 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -3149,6 +3149,7 @@ struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsign
>         unsigned tgid;
>         struct proc_fs_info *fs_info = proc_sb(dir->i_sb);
>         struct pid_namespace *ns = fs_info->pid_ns;
> +       int limit_pids = proc_fs_limit_pids(fs_info);

Shouldn't the addition of proc_fs_limit_pids() be in this patch?

Also, can we name it something self-documented?
"ptraceable_pids_only=1", perhaps?  Or even pids=ptraceable (as
opposed to pids=all or maybe other choices in the future)?

--Andy

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