From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753072AbZHCJIK (ORCPT ); Mon, 3 Aug 2009 05:08:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751665AbZHCJIJ (ORCPT ); Mon, 3 Aug 2009 05:08:09 -0400 Received: from mail-px0-f201.google.com ([209.85.216.201]:41444 "EHLO mail-px0-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751634AbZHCJII (ORCPT ); Mon, 3 Aug 2009 05:08:08 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:content-transfer-encoding :in-reply-to:user-agent; b=CV2G5p2li9BmvGTUk37O6ar1glzRKaqg1ogdo83iN+kq/UfY0fZ+PzP8iLE9o7NuOz fa0ABU8XpHQHK12Bki2wk4kW0TC7kV3XjhNbyjOLbB9Rkz2YHWInx+RUW5xKfS1xdsek uk/vgeMG/0KcLgdYZeMPy4ZrEIdnqyQtCr+Jo= Date: Mon, 3 Aug 2009 17:10:19 +0800 From: Amerigo Wang To: KAMEZAWA Hiroyuki Cc: Amerigo Wang , Mike Smith , Andrew Morton , bugzilla-daemon@bugzilla.kernel.org, bugme-daemon@bugzilla.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [BUGFIX][PATCH 1/3] fix vread/vwrite to be aware of memory hole Message-ID: <20090803091019.GC6016@cr0.nay.redhat.com> References: <20090728160527.1da52682.akpm@linux-foundation.org> <20090729084825.1363c880.kamezawa.hiroyu@jp.fujitsu.com> <525c5a6c0907281946t249ef288v77ee94edd16f054@mail.gmail.com> <20090729123209.690baa48.kamezawa.hiroyu@jp.fujitsu.com> <20090731160748.279845da.kamezawa.hiroyu@jp.fujitsu.com> <20090731161128.347216e6.kamezawa.hiroyu@jp.fujitsu.com> <20090731095705.GD5048@cr0.nay.redhat.com> <65d1a0e3dc0e5fa357f392f0552b4519.squirrel@webmail-b.css.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <65d1a0e3dc0e5fa357f392f0552b4519.squirrel@webmail-b.css.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 31, 2009 at 07:32:15PM +0900, KAMEZAWA Hiroyuki wrote: >Amerigo Wang さんは書きました： >> On Fri, Jul 31, 2009 at 04:11:28PM +0900, KAMEZAWA Hiroyuki wrote: >>>From: KAMEZAWA Hiroyuki >>> >>>vread/vwrite access vmalloc area without checking there is a page or not. >>> >>>In old ages, the caller of get_vm_ara() is only IOREMAP and there is no >>>memory hole within vm_struct's [addr...addr + size - PAGE_SIZE] >>>( -PAGE_SIZE is for a guard page.) >>> >>>After per-cpu-alloc patch, it uses get_vm_area() for reserve continuous >>>virtual address but remap _later_. There tend to be a hole in valid >>> vmalloc >>>area in vm_struct lists. >>>Then, skip the hole (not mapped page) is necessary. >>>This patch updates vread/vwrite() for avoiding memory hole. >>> >>>Routines which access vmalloc area without knowing for which addr is used >>>are >>> - /proc/kcore >>> - /dev/kmem >>> >>>kcore checks IOREMAP, /dev/kmem doesn't. After this patch, IOREMAP is >>>checked and /dev/kmem will avoid to read/write it. >>>Fixes to /proc/kcore will be in the next patch in series. >>> >>>And, this itself fixes the bug as >>># dd if=/dev/kmem of=/dev/null bs=1024 count=1048576 skip=3145728 >>>can cause panic. >> >> >> What panic? :-) Would you mind to put it here? >> >It directly reboot ;( and no log. >plz try. I tried it on an x86_64 machine, no panic, just: dd: reading `/dev/kmem': Bad address Only appears on i386? :) >>>- return buf - buf_start; >>>+ >>>+ if (buf == buf_start) >>>+ return 0; >>>+ /* zero-fill memory holes */ >>>+ if (buf != buf_start + buflen) >>>+ memset(buf, 0, buflen - (buf - buf_start)); >> >> >> Is this necessary? >> >I wrote "filled by zero" and thinks it's sane, then does this. >Now, /proc/kcore allocates memory by kzalloc(), this is redundant. >/dev/kmem doesn't do that. OK. >ouch.. > >Thank you for review. >I'm sorry that new version will not appear until next week. >I can't access x86-32 in the weekend. No problem, feel free to do it at any time that is convinient for you. Thanks.