From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262042AbTEHTEy (ORCPT ); Thu, 8 May 2003 15:04:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262050AbTEHTEy (ORCPT ); Thu, 8 May 2003 15:04:54 -0400 Received: from phoenix.infradead.org ([195.224.96.167]:64775 "EHLO phoenix.infradead.org") by vger.kernel.org with ESMTP id S262042AbTEHTEx (ORCPT ); Thu, 8 May 2003 15:04:53 -0400 Date: Thu, 8 May 2003 20:17:29 +0100 From: Christoph Hellwig To: Jesse Pollard Cc: Terje Malmedal , hch@infradead.org, alan@lxorguk.ukuu.org.uk, terje.eggestad@scali.com, arjanv@redhat.com, linux-kernel@vger.kernel.org, D.A.Fedorov@inp.nsk.su Subject: Re: The disappearing sys_call_table export. Message-ID: <20030508201729.A19556@infradead.org> Mail-Followup-To: Christoph Hellwig , Jesse Pollard , Terje Malmedal , alan@lxorguk.ukuu.org.uk, terje.eggestad@scali.com, arjanv@redhat.com, linux-kernel@vger.kernel.org, D.A.Fedorov@inp.nsk.su References: <03050813134901.09468@tabby> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <03050813134901.09468@tabby>; from jesse@cats-chateau.net on Thu, May 08, 2003 at 01:13:49PM -0500 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 08, 2003 at 01:13:49PM -0500, Jesse Pollard wrote: > Unless there is a LOCK on sys_call_table[SYS_fsync] another CPU could > replace the pointer between lines 3 and 4. At that point line 4 would > destroy the existing entry.. or destroy it when the original is restored, > and would NOT be restoring the one insterted. The the race in the replacement. The second race is in actually using these hooks. As soon as you examine a user pointer/address in there you're fundamentally racy vs. another thread manipulating the user address space.