Received-SPF: pass (google.com: domain of linux-kernel+bounces-159175-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Date: Thu, 25 Apr 2024 13:57:57 -0700
From: Kees Cook <keescook@chromium.org>
To: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>,
	Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] alloc_tag: Tighten file permissions on /proc/allocinfo
Message-ID: <202404251356.F694909C63@keescook>
References: <20240425200844.work.184-kees@kernel.org>
 <w6nbxvxt3itugrvtcvnayj5ducoxifwbffd7qh6vcastw77mse@2ugphwusgttz>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <w6nbxvxt3itugrvtcvnayj5ducoxifwbffd7qh6vcastw77mse@2ugphwusgttz>

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