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

[Vasiliy Kulikov <segoon@openwall.com>]

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@openwall.com>
> CC: Kees Cook <kees@ubuntu.com>
> CC: Dave Hansen <dave@linux.vnet.ibm.com>
> CC: Christoph Lameter <cl@gentwo.org>
> CC: Pekka Enberg <penberg@cs.helsinki.fi>
> CC: Valdis.Kletnieks@vt.edu
> CC: Linus Torvalds <torvalds@linux-foundation.org>
> CC: David Rientjes <rientjes@google.com>
> CC: Alan Cox <alan@linux.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