From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750723AbVHPXHE (ORCPT ); Tue, 16 Aug 2005 19:07:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750724AbVHPXHE (ORCPT ); Tue, 16 Aug 2005 19:07:04 -0400 Received: from clock-tower.bc.nu ([81.2.110.250]:2475 "EHLO localhost.localdomain") by vger.kernel.org with ESMTP id S1750723AbVHPXHC (ORCPT ); Tue, 16 Aug 2005 19:07:02 -0400 Subject: Re: [PATCH] Fix mmap_kmem (was: [question] What's the difference between /dev/kmem and /dev/mem) From: Alan Cox To: Greg Edwards Cc: Arjan van de Ven , Linus Torvalds , Steven Rostedt , LKML , Andrew Morton , Jack Steiner In-Reply-To: <20050816221223.GA9991@sgi.com> References: <1123796188.17269.127.camel@localhost.localdomain> <1123809302.17269.139.camel@localhost.localdomain> <1123951810.3187.20.camel@laptopd505.fenrus.org> <1123953924.3187.22.camel@laptopd505.fenrus.org> <1123957087.3187.31.camel@laptopd505.fenrus.org> <20050816221223.GA9991@sgi.com> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Wed, 17 Aug 2005 00:33:45 +0100 Message-Id: <1124235225.25433.1.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.2.2 (2.2.2-5) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Maw, 2005-08-16 at 17:12 -0500, Greg Edwards wrote: > mmap_mem suffers from a lack of proper checks as well. For example, on > Altix page 0 of each node is reserved for prom and a read or write to it > will cause an MCA. mmaping /dev/mem with offset 0 will nicely explode. > Would adding a pfn_valid test in mmap_mem be the best bet, or could we > consolidate the checks currently in mmap_kmem into mmap_mem? If you use /dev/mem you should know what you are doing. Even with "checks" dd if=/dev/zero of=/dev/mem will do bad things. Trapping obviously bad cases is fine, but complete sanity checking may actually be counter productive.