From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 88B79C41514 for ; Sat, 24 Aug 2019 22:39:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6045B206BB for ; Sat, 24 Aug 2019 22:39:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728272AbfHXWjL (ORCPT ); Sat, 24 Aug 2019 18:39:11 -0400 Received: from verein.lst.de ([213.95.11.211]:37672 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727907AbfHXWjK (ORCPT ); Sat, 24 Aug 2019 18:39:10 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id BB04B68B02; Sun, 25 Aug 2019 00:39:07 +0200 (CEST) Date: Sun, 25 Aug 2019 00:39:07 +0200 From: Christoph Hellwig To: Ralph Campbell Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, =?iso-8859-1?B?Suly9G1l?= Glisse , Jason Gunthorpe , Andrew Morton , Christoph Hellwig Subject: Re: [PATCH 2/2] mm/hmm: hmm_range_fault() infinite loop Message-ID: <20190824223907.GB21891@lst.de> References: <20190823221753.2514-1-rcampbell@nvidia.com> <20190823221753.2514-3-rcampbell@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190823221753.2514-3-rcampbell@nvidia.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 23, 2019 at 03:17:53PM -0700, Ralph Campbell wrote: > Normally, callers to handle_mm_fault() are supposed to check the > vma->vm_flags first. hmm_range_fault() checks for VM_READ but doesn't > check for VM_WRITE if the caller requests a page to be faulted in > with write permission (via the hmm_range.pfns[] value). > If the vma is write protected, this can result in an infinite loop: > hmm_range_fault() > walk_page_range() > ... > hmm_vma_walk_hole() > hmm_vma_walk_hole_() > hmm_vma_do_fault() > handle_mm_fault(FAULT_FLAG_WRITE) > /* returns VM_FAULT_WRITE */ > /* returns -EBUSY */ > /* returns -EBUSY */ > /* returns -EBUSY */ > /* loops on -EBUSY and range->valid */ > Prevent this by checking for vma->vm_flags & VM_WRITE before calling > handle_mm_fault(). > > Signed-off-by: Ralph Campbell Looks good, Reviewed-by: Christoph Hellwig