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

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Date: Thu, 25 Apr 2024 17:45:54 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Suren Baghdasaryan <surenb@...gle.com>, 
	Matthew Wilcox <willy@...radead.org>, Kees Cook <keescook@...omium.org>, 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, Apr 25, 2024 at 02:38:42PM -0700, Andrew Morton wrote:
> On Thu, 25 Apr 2024 14:21:39 -0700 Suren Baghdasaryan <surenb@...gle.com> wrote:
> 
> > > > > The side effect of locking down more and more reporting interfaces is
> > > > > that programs that consume those interfaces now have to run as root.
> > > >
> > > > sudo cat /proc/allocinfo | analyse-that-fie
> > >
> > > Even that is still an annoyance, but I'm thinking more about a future
> > > daemon to collect this every n seconds - that really shouldn't need to
> > > be root.
> > 
> > Yeah, that would preclude some nice usecases. Could we maybe use
> > CAP_SYS_ADMIN checks instead? That way we can still use it from a
> > non-root process?
> 
> I'm inclined to keep Kees's 0400.  Yes it's a hassle but security is
> always a hassle.  Let's not make Linux less secure, especially for
> people who aren't even using /proc/allocinfo.

That's a bit too trite; we've seen often enough that putting security
above all other concerns leads to worse outcomes in the long run; impair
usability too much and you're just causing more problems than you solve.

We need to take a balanced approach, like with everything else we do.

I'd really like to hear from Kees why pre-sorting the output so we aren't
leaking kernel image details wouldn't be sufficient.