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

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Message-ID: <Zitmm2SWucJA1Bdb@duo.ucw.cz>
Date: Fri, 26 Apr 2024 10:32:27 +0200
From: Pavel Machek <pavel@....cz>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: Kent Overstreet <kent.overstreet@...ux.dev>,
	Matthew Wilcox <willy@...radead.org>,
	Kees Cook <keescook@...omium.org>,
	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

Hi!

> > > > > 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.
> > > >
> > > > Err...
> > > >
> > > > 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?

CAP_SYS_ADMIN is really not suitable, as it can do changes to the
system. On working system, allocinfo is really not dangerous, it just
may make exploits harder. CAP_KERNEL_OBSERVER or something...

								Pavel
-- 
People of Russia, stop Putin before his war on Ukraine escalates.

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