Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755412AbaBTSOt (ORCPT ); Thu, 20 Feb 2014 13:14:49 -0500 Received: from mx1.redhat.com ([209.132.183.28]:10665 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754106AbaBTSOs (ORCPT ); Thu, 20 Feb 2014 13:14:48 -0500 Date: Thu, 20 Feb 2014 13:14:40 -0500 From: Dave Jones To: Mateusz Guzik Cc: linux-kernel@vger.kernel.org, Rik van Riel Subject: Re: [PATCH] kref: oops on zero or negative refcount Message-ID: <20140220181440.GA31506@redhat.com> Mail-Followup-To: Dave Jones , Mateusz Guzik , linux-kernel@vger.kernel.org, Rik van Riel References: <1392918299-673-1-git-send-email-mguzik@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1392918299-673-1-git-send-email-mguzik@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 20, 2014 at 06:44:59PM +0100, Mateusz Guzik wrote: > In use after free situations, it is possible for one thread to write to > memory that has just been reallocated to a new user. This could open up > potential security issues. > > diff --git a/include/linux/kref.h b/include/linux/kref.h > index 484604d..c3f8a0a 100644 > --- a/include/linux/kref.h > +++ b/include/linux/kref.h > @@ -43,8 +43,10 @@ static inline void kref_get(struct kref *kref) > /* If refcount was 0 before incrementing then we have a race > * condition when this kref is freeing by some other thread right now. > * In this case one should use kref_get_unless_zero() > + * > + * Terminate the current thread to stop potential security exploits. > */ > - WARN_ON_ONCE(atomic_inc_return(&kref->refcount) < 2); > + BUG_ON(atomic_inc_return(&kref->refcount) < 2); This isn't "terminating the thread", this is "lock up the box". Dave -- 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/