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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 37103C43461 for ; Mon, 7 Sep 2020 15:16:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 038F821481 for ; Mon, 7 Sep 2020 15:16:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730086AbgIGPQi (ORCPT ); Mon, 7 Sep 2020 11:16:38 -0400 Received: from mx01.bbu.dsd.mx.bitdefender.com ([91.199.104.161]:43950 "EHLO mx01.bbu.dsd.mx.bitdefender.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730081AbgIGPQc (ORCPT ); Mon, 7 Sep 2020 11:16:32 -0400 Received: from smtp.bitdefender.com (smtp02.buh.bitdefender.net [10.17.80.76]) by mx01.bbu.dsd.mx.bitdefender.com (Postfix) with ESMTPS id 922FF30747BE; Mon, 7 Sep 2020 18:16:03 +0300 (EEST) Received: from localhost (unknown [195.189.155.252]) by smtp.bitdefender.com (Postfix) with ESMTPSA id 679503038E24; Mon, 7 Sep 2020 18:16:03 +0300 (EEST) From: Adalbert =?iso-8859-2?b?TGF643I=?= Subject: Re: [RESEND RFC PATCH 4/5] mm/remote_mapping: use a pidfd to access memory belonging to unrelated process To: Oleg Nesterov Cc: linux-mm@kvack.org, linux-api@vger.kernel.org, Andrew Morton , Alexander Graf , Stefan Hajnoczi , Jerome Glisse , Paolo Bonzini , Mihai =?UTF-8?b?RG9uyJt1?= , Mircea Cirjaliu , Andy Lutomirski , Arnd Bergmann , Sargun Dhillon , Aleksa Sarai , Jann Horn , Kees Cook , Matthew Wilcox , Christian Brauner In-Reply-To: <20200907143008.GB31050@redhat.com> References: <20200904113116.20648-1-alazar@bitdefender.com> <20200904113116.20648-5-alazar@bitdefender.com> <20200907143008.GB31050@redhat.com> Date: Mon, 07 Sep 2020 18:16:30 +0300 Message-ID: <15994917900.dEaCB.18501@host> User-agent: void Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit MIME-Version: 1.0 Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Mon, 7 Sep 2020 16:30:08 +0200, Oleg Nesterov wrote: > it seems that nobody is going to review this patch ;) > > So I tried to read mirror_vm_fault() and the usage of mmap_sem doesn't > look right to me. But let me repeat, this is not my area I can be easily > wrong, please correct me. > > On 09/04, Adalbert Lazăr wrote: > > > > +static vm_fault_t mirror_vm_fault(struct vm_fault *vmf) > > +{ > > + struct vm_area_struct *vma = vmf->vma; > > + struct mm_struct *mm = vma->vm_mm; > > + struct remote_vma_context *ctx = vma->vm_private_data; > > + struct remote_view *view = ctx->view; > > + struct file *file = vma->vm_file; > > + struct remote_file_context *fctx = file->private_data; > > + unsigned long req_addr; > > + unsigned int gup_flags; > > + struct page *req_page; > > + vm_fault_t result = VM_FAULT_SIGBUS; > > + struct mm_struct *src_mm = fctx->mm; > > + unsigned long seq; > > + int idx; > > + > > +fault_retry: > > + seq = mmu_interval_read_begin(&view->mmin); > > + > > + idx = srcu_read_lock(&fctx->fault_srcu); > > + > > + /* check if view was invalidated */ > > + if (unlikely(!READ_ONCE(view->valid))) { > > + pr_debug("%s: region [%lx-%lx) was invalidated!!\n", __func__, > > + view->offset, view->offset + view->size); > > + goto out_invalid; /* VM_FAULT_SIGBUS */ > > + } > > + > > + /* drop current mm semapchore */ > > + up_read(¤t->mm->mmap_sem); > > Please use mmap_read_lock/unlock(mm) instead of down/up_read(mmap_sem). This patch series is based on 5.7-rc2. The cover letter has base-commit: present, but I forgot to mention this explicitly, sorry. Adalbert