linux-hardening - Re: [PATCH] alloc_tag: Tighten file permissions on /proc/allocinfo

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Date: Thu, 25 Apr 2024 16:47:18 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Kees Cook <keescook@...omium.org>
Cc: Kent Overstreet <kent.overstreet@...ux.dev>, Matthew Wilcox
 <willy@...radead.org>, Suren Baghdasaryan <surenb@...gle.com>,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH] alloc_tag: Tighten file permissions on /proc/allocinfo

On Thu, 25 Apr 2024 15:42:30 -0700 Kees Cook <keescook@...omium.org> wrote:

> > The concern about leaking image layout could be addressed by sorting the
> > output before returning to userspace.
> 
> It's trivial to change permissions from the default 0400 at boot time.
> It can even have groups and ownership changed, etc. This is why we have
> per-mount-namespace /proc instances:
> 
> # chgrp sysmonitor /proc/allocinfo
> # chmod 0440 /proc/allocinfo
> 
> Poof, instant role-based access control. :)

Conversely, the paranoid could set it to 0400 at boot also.

> I'm just trying to make the _default_ safe.

Agree with this.

Semi-seriously, how about we set the permissions to 0000 and force
distributors/users to make a decision.