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 84FBDC43461 for ; Mon, 7 Sep 2020 15:16:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 01D2621741 for ; Mon, 7 Sep 2020 15:16:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 01D2621741 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=bitdefender.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 43BE56B0003; Mon, 7 Sep 2020 11:16:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3C5C86B0037; Mon, 7 Sep 2020 11:16:08 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2B4E46B0055; Mon, 7 Sep 2020 11:16:08 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0125.hostedemail.com [216.40.44.125]) by kanga.kvack.org (Postfix) with ESMTP id 127456B0003 for ; Mon, 7 Sep 2020 11:16:08 -0400 (EDT) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id CC6F5180AD81A for ; Mon, 7 Sep 2020 15:16:07 +0000 (UTC) X-FDA: 77236615974.20.light30_0c09186270cd Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin20.hostedemail.com (Postfix) with ESMTP id 96CB9180C07AB for ; Mon, 7 Sep 2020 15:16:07 +0000 (UTC) X-HE-Tag: light30_0c09186270cd X-Filterd-Recvd-Size: 3505 Received: from mx01.bbu.dsd.mx.bitdefender.com (mx01.bbu.dsd.mx.bitdefender.com [91.199.104.161]) by imf17.hostedemail.com (Postfix) with ESMTP for ; Mon, 7 Sep 2020 15:16:06 +0000 (UTC) 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 MIME-Version: 1.0 X-Rspamd-Queue-Id: 96CB9180C07AB X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 7 Sep 2020 16:30:08 +0200, Oleg Nesterov wrote: > it seems that nobody is going to review this patch ;) >=20 > 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 easil= y > wrong, please correct me. >=20 > On 09/04, Adalbert Laz=C4=83r wrote: > > > > +static vm_fault_t mirror_vm_fault(struct vm_fault *vmf) > > +{ > > + struct vm_area_struct *vma =3D vmf->vma; > > + struct mm_struct *mm =3D vma->vm_mm; > > + struct remote_vma_context *ctx =3D vma->vm_private_data; > > + struct remote_view *view =3D ctx->view; > > + struct file *file =3D vma->vm_file; > > + struct remote_file_context *fctx =3D file->private_data; > > + unsigned long req_addr; > > + unsigned int gup_flags; > > + struct page *req_page; > > + vm_fault_t result =3D VM_FAULT_SIGBUS; > > + struct mm_struct *src_mm =3D fctx->mm; > > + unsigned long seq; > > + int idx; > > + > > +fault_retry: > > + seq =3D mmu_interval_read_begin(&view->mmin); > > + > > + idx =3D 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); >=20 > 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