linux-kernel - Re: [PATCH 2/2] mm: restrict access to /proc/meminfo

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Message-ID: <20110927193810.GA5416@albatros>
Date:	Tue, 27 Sep 2011 23:38:10 +0400
From:	Vasiliy Kulikov <segoon@...nwall.com>
To:	kernel-hardening@...ts.openwall.com,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	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 2/2] mm: restrict access to /proc/meminfo

On Tue, Sep 27, 2011 at 21:56 +0400, Vasiliy Kulikov wrote:
> /proc/meminfo stores information related to memory pages usage, which
> may be used to monitor the number of objects in specific caches (and/or
> the changes of these numbers).  This might reveal private information
> similar to /proc/slabinfo infoleaks.  To remove the infoleak, just
> restrict meminfo to root.  If it is used by unprivileged daemons,
> meminfo permissions can be altered the same way as slabinfo:
> 
>     groupadd meminfo
>     usermod -a -G meminfo $MONITOR_USER
>     chmod g+r /proc/meminfo
>     chgrp meminfo /proc/meminfo

Just to make it clear: since this patch breaks "free", I don't propose
it anymore.


> Signed-off-by: Vasiliy Kulikov <segoon@...nwall.com>
> CC: Kees Cook <kees@...ntu.com>
> CC: Dave Hansen <dave@...ux.vnet.ibm.com>
> CC: Christoph Lameter <cl@...two.org>
> CC: Pekka Enberg <penberg@...helsinki.fi>
> CC: Valdis.Kletnieks@...edu
> CC: Linus Torvalds <torvalds@...ux-foundation.org>
> CC: David Rientjes <rientjes@...gle.com>
> CC: Alan Cox <alan@...ux.intel.com>
> ---
>  fs/proc/meminfo.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> --
> diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
> index 5861741..949bdee 100644
> --- a/fs/proc/meminfo.c
> +++ b/fs/proc/meminfo.c
> @@ -187,7 +187,7 @@ static const struct file_operations meminfo_proc_fops = {
>  
>  static int __init proc_meminfo_init(void)
>  {
> -	proc_create("meminfo", 0, NULL, &meminfo_proc_fops);
> +	proc_create("meminfo", S_IFREG | S_IRUSR, NULL, &meminfo_proc_fops);
>  	return 0;
>  }
>  module_init(proc_meminfo_init);

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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