From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761405AbZFXQsH (ORCPT ); Wed, 24 Jun 2009 12:48:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760790AbZFXQrz (ORCPT ); Wed, 24 Jun 2009 12:47:55 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:56246 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758772AbZFXQry (ORCPT ); Wed, 24 Jun 2009 12:47:54 -0400 Date: Wed, 24 Jun 2009 09:46:59 -0700 (PDT) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Thomas Gleixner cc: LKML , Ingo Molnar , Peter Zijlstra , Darren Hart Subject: Re: [PATCH V2] futex: Fix the write access fault problem for real In-Reply-To: Message-ID: References: User-Agent: Alpine 2.01 (LFD 1184 2008-12-16) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 24 Jun 2009, Thomas Gleixner wrote: > > The solution is to not rely on access_ok and get_user() for any write > access related fault on private and shared futexes. Instead we need to > fault it in with verification of write access. > > There is no generic non destructive write mechanism which would fault > the user page in trough a #PF, but as we already know that we will > fault we can as well call get_user_pages() directly and avoid the #PF > overhead. Ack. Patch looks saner this way, and the commit message explains the issues. Linus