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

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Date: Thu, 25 Apr 2024 13:57:57 -0700
From: Kees Cook <keescook@...omium.org>
To: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: Suren Baghdasaryan <surenb@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.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 04:45:51PM -0400, Kent Overstreet wrote:
> On Thu, Apr 25, 2024 at 01:08:50PM -0700, Kees Cook wrote:
> > The /proc/allocinfo file exposes a tremendous about of information about
> > kernel build details, memory allocations (obviously), and potentially
> > even image layout (due to ordering). As this is intended to be consumed
> > by system owners (like /proc/slabinfo), use the same file permissions as
> > there: 0400.
> 
> The side effect of locking down more and more reporting interfaces is
> that programs that consume those interfaces now have to run as root.

I'm fine if you want to tie it to some existing capability, but it
shouldn't be world-readable. Also, plenty of diagnostic tools already
either run as root or open whatever files they need to before dropping
privs.

-- 
Kees Cook