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=-6.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 5A450C433FF for ; Mon, 29 Jul 2019 08:33:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 26272206E0 for ; Mon, 29 Jul 2019 08:33:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Yj2x/YP+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727733AbfG2IdJ (ORCPT ); Mon, 29 Jul 2019 04:33:09 -0400 Received: from mail-lf1-f68.google.com ([209.85.167.68]:41026 "EHLO mail-lf1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726305AbfG2IdJ (ORCPT ); Mon, 29 Jul 2019 04:33:09 -0400 Received: by mail-lf1-f68.google.com with SMTP id 62so36568667lfa.8 for ; Mon, 29 Jul 2019 01:33:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=fzjgi5IYwtgWKCD94QQKl1WKdW6R14NVG7cIaq5hNd0=; b=Yj2x/YP+GQx3u0ETLl95DFn76V+nUeZ0HgcyvoUS0J23BQZRtMVjzIjCk80uAnKs7Q HQlRZ1Ixt54mk2Xl0CPAS4hhA/sUUWDDv5/rRB2v+KHQ4C83QqlXf3PwcGVgrK44gXGK T8QwJf/xyMFHhs2/N13YRy+O5ZrAaWHzCrT+9uVBY8T0e9XoY4vKw0aMc3l5RNtlaUye 2VNkfpFLe1kIUERcSgFAVPZYdYW3WF1u+Y7yXdwTmDoI1JjojonOcWFQNJEu9zZ2L+Ms iR7gq/NDAQVjh7NAv7l7QBoZvm7uLNemt8yUQrhf5sdM60rK76dfCnEyAtS40qTLkvPy d9ag== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=fzjgi5IYwtgWKCD94QQKl1WKdW6R14NVG7cIaq5hNd0=; b=qFqFX15699i5pVKnmvmgp6xCheXTbEIccEl9xPnjqstv88w2yDNg3Ov/52XHsUbZGk oMQD6c4Tj3CjOgr8joXF+IQ6XT8VEfKJi+RxMcdoKARh3USoL1JzTxLNaikXCN3Kt7Ng Mib1VbA4Eqw83Muf1G4HTXJ9sEzfDxtE/7yfj5osmn71avUjdNsiCrqekPabTmpY90ck bHBVuGWQywtfV7NEiSVOWpJ3HXXeq9s6j0v2wqbrvAbDT0s7P2ge0wclJhTFrQqevcX4 VzZsXfJ71p9sdVNq7VnFcsByxj3jsC+K4N8Y8lM919YIdCSO95anD7EkROXlX8KHnE3n rI3g== X-Gm-Message-State: APjAAAXu6R9o9H/Qac5peR9b6BOxxUAAGGPFUBTe3HY0MB9XVuvYBbap gPapBjODt/sL9nI93mr9XNhmwNpCL93Hg2+Lz5FHFw== X-Google-Smtp-Source: APXvYqxOB3hlBmp/ELmfdAvewRmPGBGlLy908aDcnO5gzCSlHvcgEUZGOZj5/xu4Z+SD47jako1Nt3Hob11dDINtGdM= X-Received: by 2002:a19:5e10:: with SMTP id s16mr49683043lfb.13.1564389186319; Mon, 29 Jul 2019 01:33:06 -0700 (PDT) MIME-Version: 1.0 References: <20190215024830.GA26477@jordon-HP-15-Notebook-PC> <20190728180611.GA20589@mail-itl> In-Reply-To: From: Souptick Joarder Date: Mon, 29 Jul 2019 14:02:54 +0530 Message-ID: Subject: Re: [Xen-devel] [PATCH v4 8/9] xen/gntdev.c: Convert to use vm_map_pages() To: =?UTF-8?Q?Marek_Marczykowski=2DG=C3=B3recki?= Cc: Andrew Morton , Matthew Wilcox , Michal Hocko , Boris Ostrovsky , Juergen Gross , Russell King - ARM Linux , robin.murphy@arm.com, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, Linux-MM Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 29, 2019 at 1:35 PM Souptick Joarder wro= te: > > On Sun, Jul 28, 2019 at 11:36 PM Marek Marczykowski-G=C3=B3recki > wrote: > > > > On Fri, Feb 15, 2019 at 08:18:31AM +0530, Souptick Joarder wrote: > > > Convert to use vm_map_pages() to map range of kernel > > > memory to user vma. > > > > > > map->count is passed to vm_map_pages() and internal API > > > verify map->count against count ( count =3D vma_pages(vma)) > > > for page array boundary overrun condition. > > > > This commit breaks gntdev driver. If vma->vm_pgoff > 0, vm_map_pages > > will: > > - use map->pages starting at vma->vm_pgoff instead of 0 > > The actual code ignores vma->vm_pgoff > 0 scenario and mapped > the entire map->pages[i]. Why the entire map->pages[i] needs to be mapped > if vma->vm_pgoff > 0 (in original code) ? > > are you referring to set vma->vm_pgoff =3D 0 irrespective of value passed > from user space ? If yes, using vm_map_pages_zero() is an alternate > option. > > > > - verify map->count against vma_pages()+vma->vm_pgoff instead of just > > vma_pages(). > > In original code -> > > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c > index 559d4b7f807d..469dfbd6cf90 100644 > --- a/drivers/xen/gntdev.c > +++ b/drivers/xen/gntdev.c > @@ -1084,7 +1084,7 @@ static int gntdev_mmap(struct file *flip, struct > vm_area_struct *vma) > int index =3D vma->vm_pgoff; > int count =3D vma_pages(vma); > > Count is user passed value. > > struct gntdev_grant_map *map; > - int i, err =3D -EINVAL; > + int err =3D -EINVAL; > if ((vma->vm_flags & VM_WRITE) && !(vma->vm_flags & VM_SHARED)) > return -EINVAL; > @@ -1145,12 +1145,9 @@ static int gntdev_mmap(struct file *flip, > struct vm_area_struct *vma) > goto out_put_map; > if (!use_ptemod) { > - for (i =3D 0; i < count; i++) { > - err =3D vm_insert_page(vma, vma->vm_start + i*PAGE_SIZE, > - map->pages[i]); > > and when count > i , we end up with trying to map memory outside > boundary of map->pages[i], which was not correct. typo. s/count > i / count > map->count > > - if (err) > - goto out_put_map; > - } > + err =3D vm_map_pages(vma, map->pages, map->count); > + if (err) > + goto out_put_map; > > With this commit, inside __vm_map_pages(), we have addressed this scenari= o. > > +static int __vm_map_pages(struct vm_area_struct *vma, struct page **page= s, > + unsigned long num, unsigned long offset) > +{ > + unsigned long count =3D vma_pages(vma); > + unsigned long uaddr =3D vma->vm_start; > + int ret, i; > + > + /* Fail if the user requested offset is beyond the end of the object */ > + if (offset > num) > + return -ENXIO; > + > + /* Fail if the user requested size exceeds available object size */ > + if (count > num - offset) > + return -ENXIO; > > By checking count > num -offset. (considering vma->vm_pgoff !=3D 0 as wel= l). > So we will never cross the boundary of map->pages[i]. > > > > > > In practice, this breaks using a single gntdev FD for mapping multiple > > grants. > > How ? > > > > > It looks like vm_map_pages() is not a good fit for this code and IMO it > > should be reverted. > > Did you hit any issue around this code in real time ? > > > > > > > Signed-off-by: Souptick Joarder > > > Reviewed-by: Boris Ostrovsky > > > --- > > > drivers/xen/gntdev.c | 11 ++++------- > > > 1 file changed, 4 insertions(+), 7 deletions(-) > > > > > > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c > > > index 5efc5ee..5d64262 100644 > > > --- a/drivers/xen/gntdev.c > > > +++ b/drivers/xen/gntdev.c > > > @@ -1084,7 +1084,7 @@ static int gntdev_mmap(struct file *flip, struc= t vm_area_struct *vma) > > > int index =3D vma->vm_pgoff; > > > int count =3D vma_pages(vma); > > > struct gntdev_grant_map *map; > > > - int i, err =3D -EINVAL; > > > + int err =3D -EINVAL; > > > > > > if ((vma->vm_flags & VM_WRITE) && !(vma->vm_flags & VM_SHARED)) > > > return -EINVAL; > > > @@ -1145,12 +1145,9 @@ static int gntdev_mmap(struct file *flip, stru= ct vm_area_struct *vma) > > > goto out_put_map; > > > > > > if (!use_ptemod) { > > > - for (i =3D 0; i < count; i++) { > > > - err =3D vm_insert_page(vma, vma->vm_start + i*P= AGE_SIZE, > > > - map->pages[i]); > > > - if (err) > > > - goto out_put_map; > > > - } > > > + err =3D vm_map_pages(vma, map->pages, map->count); > > > + if (err) > > > + goto out_put_map; > > > } else { > > > #ifdef CONFIG_X86 > > > /* > > > > -- > > Best Regards, > > Marek Marczykowski-G=C3=B3recki > > Invisible Things Lab > > A: Because it messes up the order in which people normally read text. > > Q: Why is top-posting such a bad thing?