linux-kernel - Re: [PATCH] mm: reorder can_do

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Date:	Mon, 2 Mar 2015 13:49:45 -0800
From:	Nick Kralevich <nnk@...gle.com>
To:	Jeff Vander Stoep <jeffv@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Paul Cassella <cassella@...y.com>, linux-mm@...ck.org,
	lkml <linux-kernel@...r.kernel.org>,
	Stephen Smalley <sds@...ho.nsa.gov>
Subject: Re: [PATCH] mm: reorder can_do_mlock to fix audit denial

On Mon, Mar 2, 2015 at 9:20 AM, Jeff Vander Stoep <jeffv@...gle.com> wrote:
> A userspace call to mmap(MAP_LOCKED) may result in the successful
> locking of memory while also producing a confusing audit log denial.
> can_do_mlock checks capable and rlimit. If either of these return
> positive can_do_mlock returns true. The capable check leads to an LSM
> hook used by apparmour and selinux which produce the audit denial.
> Reordering so rlimit is checked first eliminates the denial on success,
> only recording a denial when the lock is unsuccessful as a result of
> the denial.
>

Acked-By: Nick Kralevich <nnk@...gle.com>

> Signed-off-by: Jeff Vander Stoep <jeffv@...gle.com>
> ---
>  mm/mlock.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/mlock.c b/mm/mlock.c
> index 73cf098..8a54cd2 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -26,10 +26,10 @@
>
>  int can_do_mlock(void)
>  {
> -       if (capable(CAP_IPC_LOCK))
> -               return 1;
>         if (rlimit(RLIMIT_MEMLOCK) != 0)
>                 return 1;
> +       if (capable(CAP_IPC_LOCK))
> +               return 1;
>         return 0;
>  }
>  EXPORT_SYMBOL(can_do_mlock);
> --
> 2.2.0.rc0.207.ga3a616c
>



-- 
Nick Kralevich | Android Security | nnk@...gle.com | 650.214.4037
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