From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964858AbWCGXKS (ORCPT ); Tue, 7 Mar 2006 18:10:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964859AbWCGXKS (ORCPT ); Tue, 7 Mar 2006 18:10:18 -0500 Received: from smtp.osdl.org ([65.172.181.4]:38363 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S964858AbWCGXKQ (ORCPT ); Tue, 7 Mar 2006 18:10:16 -0500 Date: Tue, 7 Mar 2006 15:12:00 -0800 From: Andrew Morton To: Christoph Hellwig Cc: roe@sgi.com, linux-kernel@vger.kernel.org, riel@redhat.com Subject: Re: [PATCH] Prevent NULL pointer deref in grab_swap_token Message-Id: <20060307151200.7a41943a.akpm@osdl.org> In-Reply-To: <20060307224926.GA13147@infradead.org> References: <20060307211344.GA2946@sgi.com> <20060307224926.GA13147@infradead.org> X-Mailer: Sylpheed version 1.0.0 (GTK+ 1.2.10; i386-vine-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Christoph Hellwig wrote: > > On Tue, Mar 07, 2006 at 03:13:44PM -0600, Dean Roe wrote: > > grab_swap_token() assumes that the current process has an mm struct, > > which is not true for kernel threads invoking get_user_pages(). Since > > this should be extremely rare, just return from grab_swap_token() > > without doing anything. > > There's a few things that will break if a kernel thread calls > get_user_pages, so we should rather fix those. What things will break? Anything which dinks with current->mm in or under get_user_pages() is probably already broken.