linux-kernel - Re: [PATCH 1/2] mm: restrict access to slab files under procfs and sysfs

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Date:	Tue, 27 Sep 2011 14:35:25 -0500 (CDT)
From:	Christoph Lameter <cl@...two.org>
To:	Vasiliy Kulikov <segoon@...nwall.com>
cc:	kernel-hardening@...ts.openwall.com,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>, linux-mm@...ck.org,
	Kees Cook <kees@...ntu.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>, Valdis.Kletnieks@...edu,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Alan Cox <alan@...ux.intel.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm: restrict access to slab files under procfs and
 sysfs

On Tue, 27 Sep 2011, Vasiliy Kulikov wrote:

> On Tue, Sep 27, 2011 at 13:08 -0500, Christoph Lameter wrote:
> > Possible candidates:
> >
> > christoph@...y:~/n/linux-2.6$ grep proc_create mm/*
> > mm/swapfile.c:	proc_create("swaps", 0, NULL, &proc_swaps_operations);
> > mm/vmstat.c:	proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations);
> > mm/vmstat.c:	proc_create("pagetypeinfo", S_IRUGO, NULL, &pagetypeinfo_file_ops);
> > mm/vmstat.c:	proc_create("vmstat", S_IRUGO, NULL, &proc_vmstat_file_operations);
> > mm/vmstat.c:	proc_create("zoneinfo", S_IRUGO, NULL, &proc_zoneinfo_file_operations);
> >
> > vmstat and zoneinfo in particular give similar information to what is
> > revealed through the slab proc files.
>
> Do you know whether these files are actively used?  I don't want to
> break tools like "free" or "top".  In this case we'll have to discover
> another way to limit this information.

top uses per process information. Tried an strace and I see no access to
vmstat or zoneinfo.

free uses /proc/meminfo not vmstat or zoneinfo. Since you already have a
patch that limits /proc/meminfo access there is already an issue there.

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