Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754189AbYG2Ame (ORCPT ); Mon, 28 Jul 2008 20:42:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752381AbYG2Am0 (ORCPT ); Mon, 28 Jul 2008 20:42:26 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:46336 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752276AbYG2AmZ (ORCPT ); Mon, 28 Jul 2008 20:42:25 -0400 Date: Mon, 28 Jul 2008 17:39:18 -0700 (PDT) From: Linus Torvalds To: Johannes Weiner cc: Alexey Dobriyan , akpm@linuxfoundation.org, torvalds@linuxfoundation.org, npiggin@suse.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: do not overrun page table ranges in gup In-Reply-To: Message-ID: References: <20080728184947.GA5041@martell.zuzino.mipt.ru> <20080728185316.GA19479@martell.zuzino.mipt.ru> <87y73l5zlj.fsf_-_@saeurebad.de> <87tze95yrk.fsf@saeurebad.de> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) 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 Content-Length: 1366 Lines: 49 On Mon, 28 Jul 2008, Linus Torvalds wrote: > > So no, the right fix would be to align 'start' first, which means that > everything else (including 'end') will be page-aligned. Aligning just one > or the other is very very wrong. Does this work? Not pretty, but it stands _some_ chance of being correct. Linus --- arch/x86/mm/gup.c | 9 ++++++--- 1 files changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c index 3085f25..007bb06 100644 --- a/arch/x86/mm/gup.c +++ b/arch/x86/mm/gup.c @@ -223,14 +223,17 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) { struct mm_struct *mm = current->mm; - unsigned long end = start + (nr_pages << PAGE_SHIFT); - unsigned long addr = start; + unsigned long addr, len, end; unsigned long next; pgd_t *pgdp; int nr = 0; + start &= PAGE_MASK; + addr = start; + len = (unsigned long) nr_pages << PAGE_SHIFT; + end = start + len; if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, - start, nr_pages*PAGE_SIZE))) + start, len))) goto slow_irqon; /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/