Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754479Ab0BSRAU (ORCPT ); Fri, 19 Feb 2010 12:00:20 -0500 Received: from kroah.org ([198.145.64.141]:57329 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754139Ab0BSRAE (ORCPT ); Fri, 19 Feb 2010 12:00:04 -0500 X-Mailbox-Line: From gregkh@kvm.kroah.org Fri Feb 19 08:32:30 2010 Message-Id: <20100219163230.389627906@kvm.kroah.org> User-Agent: quilt/0.48-4.4 Date: Fri, 19 Feb 2010 08:28:56 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Thomas Gleixner , Darren Hart , Peter Zijlstra Subject: [03/93] futex: Handle user space corruption gracefully In-Reply-To: <20100219165717.GA15002@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1907 Lines: 55 2.6.32-stable review patch. If anyone has any objections, please let us know. ------------------ From: Thomas Gleixner commit 51246bfd189064079c54421507236fd2723b18f3 upstream. If the owner of a PI futex dies we fix up the pi_state and set pi_state->owner to NULL. When a malicious or just sloppy programmed user space application sets the futex value to 0 e.g. by calling pthread_mutex_init(), then the futex can be acquired again. A new waiter manages to enqueue itself on the pi_state w/o damage, but on unlock the kernel dereferences pi_state->owner and oopses. Prevent this by checking pi_state->owner in the unlock path. If pi_state->owner is not current we know that user space manipulated the futex value. Ignore the mess and return -EINVAL. This catches the above case and also the case where a task hijacks the futex by setting the tid value and then tries to unlock it. Reported-by: Jermome Marchand Signed-off-by: Thomas Gleixner Acked-by: Darren Hart Acked-by: Peter Zijlstra Signed-off-by: Greg Kroah-Hartman --- kernel/futex.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/kernel/futex.c +++ b/kernel/futex.c @@ -758,6 +758,13 @@ static int wake_futex_pi(u32 __user *uad if (!pi_state) return -EINVAL; + /* + * If current does not own the pi_state then the futex is + * inconsistent and user space fiddled with the futex value. + */ + if (pi_state->owner != current) + return -EINVAL; + spin_lock(&pi_state->pi_mutex.wait_lock); new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/