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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 4CE40C43441 for ; Fri, 9 Nov 2018 07:03:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 114AF20840 for ; Fri, 9 Nov 2018 07:03:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 114AF20840 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727996AbeKIQmc (ORCPT ); Fri, 9 Nov 2018 11:42:32 -0500 Received: from mx2.suse.de ([195.135.220.15]:33120 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727485AbeKIQmb (ORCPT ); Fri, 9 Nov 2018 11:42:31 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id BB3B4B003; Fri, 9 Nov 2018 07:03:17 +0000 (UTC) Subject: Re: [PATCH] xen: remove size limit of privcmd-buf mapping interface To: linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org Cc: boris.ostrovsky@oracle.com, sstabellini@kernel.org, stable@vger.kernel.org References: <20181101123307.8424-1-jgross@suse.com> From: Juergen Gross Openpgp: preference=signencrypt Autocrypt: addr=jgross@suse.com; prefer-encrypt=mutual; keydata= xsBNBFOMcBYBCACgGjqjoGvbEouQZw/ToiBg9W98AlM2QHV+iNHsEs7kxWhKMjrioyspZKOB ycWxw3ie3j9uvg9EOB3aN4xiTv4qbnGiTr3oJhkB1gsb6ToJQZ8uxGq2kaV2KL9650I1SJve dYm8Of8Zd621lSmoKOwlNClALZNew72NjJLEzTalU1OdT7/i1TXkH09XSSI8mEQ/ouNcMvIJ NwQpd369y9bfIhWUiVXEK7MlRgUG6MvIj6Y3Am/BBLUVbDa4+gmzDC9ezlZkTZG2t14zWPvx XP3FAp2pkW0xqG7/377qptDmrk42GlSKN4z76ELnLxussxc7I2hx18NUcbP8+uty4bMxABEB AAHNHkp1ZXJnZW4gR3Jvc3MgPGpncm9zc0BzdXNlLmRlPsLAeQQTAQIAIwUCU4xw6wIbAwcL CQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJELDendYovxMvi4UH/Ri+OXlObzqMANruTd4N zmVBAZgx1VW6jLc8JZjQuJPSsd/a+bNr3BZeLV6lu4Pf1Yl2Log129EX1KWYiFFvPbIiq5M5 kOXTO8Eas4CaScCvAZ9jCMQCgK3pFqYgirwTgfwnPtxFxO/F3ZcS8jovza5khkSKL9JGq8Nk czDTruQ/oy0WUHdUr9uwEfiD9yPFOGqp4S6cISuzBMvaAiC5YGdUGXuPZKXLpnGSjkZswUzY d9BVSitRL5ldsQCg6GhDoEAeIhUC4SQnT9SOWkoDOSFRXZ+7+WIBGLiWMd+yKDdRG5RyP/8f 3tgGiB6cyuYfPDRGsELGjUaTUq3H2xZgIPfOwE0EU4xwFgEIAMsx+gDjgzAY4H1hPVXgoLK8 B93sTQFN9oC6tsb46VpxyLPfJ3T1A6Z6MVkLoCejKTJ3K9MUsBZhxIJ0hIyvzwI6aYJsnOew cCiCN7FeKJ/oA1RSUemPGUcIJwQuZlTOiY0OcQ5PFkV5YxMUX1F/aTYXROXgTmSaw0aC1Jpo w7Ss1mg4SIP/tR88/d1+HwkJDVW1RSxC1PWzGizwRv8eauImGdpNnseneO2BNWRXTJumAWDD pYxpGSsGHXuZXTPZqOOZpsHtInFyi5KRHSFyk2Xigzvh3b9WqhbgHHHE4PUVw0I5sIQt8hJq 5nH5dPqz4ITtCL9zjiJsExHuHKN3NZsAEQEAAcLAXwQYAQIACQUCU4xwFgIbDAAKCRCw3p3W KL8TL0P4B/9YWver5uD/y/m0KScK2f3Z3mXJhME23vGBbMNlfwbr+meDMrJZ950CuWWnQ+d+ Ahe0w1X7e3wuLVODzjcReQ/v7b4JD3wwHxe+88tgB9byc0NXzlPJWBaWV01yB2/uefVKryAf AHYEd0gCRhx7eESgNBe3+YqWAQawunMlycsqKa09dBDL1PFRosF708ic9346GLHRc6Vj5SRA UTHnQqLetIOXZm3a2eQ1gpQK9MmruO86Vo93p39bS1mqnLLspVrL4rhoyhsOyh0Hd28QCzpJ wKeHTd0MAWAirmewHXWPco8p1Wg+V+5xfZzuQY0f4tQxvOpXpt4gQ1817GQ5/Ed/wsDtBBgB CAAgFiEEhRJncuj2BJSl0Jf3sN6d1ii/Ey8FAlrd8NACGwIAgQkQsN6d1ii/Ey92IAQZFggA HRYhBFMtsHpB9jjzHji4HoBcYbtP2GO+BQJa3fDQAAoJEIBcYbtP2GO+TYsA/30H/0V6cr/W V+J/FCayg6uNtm3MJLo4rE+o4sdpjjsGAQCooqffpgA+luTT13YZNV62hAnCLKXH9n3+ZAgJ RtAyDWk1B/0SMDVs1wxufMkKC3Q/1D3BYIvBlrTVKdBYXPxngcRoqV2J77lscEvkLNUGsu/z W2pf7+P3mWWlrPMJdlbax00vevyBeqtqNKjHstHatgMZ2W0CFC4hJ3YEetuRBURYPiGzuJXU pAd7a7BdsqWC4o+GTm5tnGrCyD+4gfDSpkOT53S/GNO07YkPkm/8J4OBoFfgSaCnQ1izwgJQ jIpcG2fPCI2/hxf2oqXPYbKr1v4Z1wthmoyUgGN0LPTIm+B5vdY82wI5qe9uN6UOGyTH2B3p hRQUWqCwu2sqkI3LLbTdrnyDZaixT2T0f4tyF5Lfs+Ha8xVMhIyzNb1byDI5FKCb Message-ID: Date: Fri, 9 Nov 2018 08:03:17 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181101123307.8424-1-jgross@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: de-DE Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ping? Jan's remark regarding de-privileged qemu is no issue as the hypercall node is being closed by the de-privilege library function. Juergen On 01/11/2018 13:33, Juergen Gross wrote: > Currently the size of hypercall buffers allocated via > /dev/xen/hypercall is limited to a default of 64 memory pages. For live > migration of guests this might be too small as the page dirty bitmask > needs to be sized according to the size of the guest. This means > migrating a 8GB sized guest is already exhausting the default buffer > size for the dirty bitmap. > > There is no sensible way to set a sane limit, so just remove it > completely. The device node's usage is limited to root anyway, so there > is no additional DOS scenario added by allowing unlimited buffers. > > While at it make the error path for the -ENOMEM case a little bit > cleaner by setting n_pages to the number of successfully allocated > pages instead of the target size. > > Fixes: c51b3c639e01f2 ("xen: add new hypercall buffer mapping device") > Cc: #4.18 > Signed-off-by: Juergen Gross > --- > drivers/xen/privcmd-buf.c | 22 ++++------------------ > 1 file changed, 4 insertions(+), 18 deletions(-) > > diff --git a/drivers/xen/privcmd-buf.c b/drivers/xen/privcmd-buf.c > index df1ed37c3269..de01a6d0059d 100644 > --- a/drivers/xen/privcmd-buf.c > +++ b/drivers/xen/privcmd-buf.c > @@ -21,15 +21,9 @@ > > MODULE_LICENSE("GPL"); > > -static unsigned int limit = 64; > -module_param(limit, uint, 0644); > -MODULE_PARM_DESC(limit, "Maximum number of pages that may be allocated by " > - "the privcmd-buf device per open file"); > - > struct privcmd_buf_private { > struct mutex lock; > struct list_head list; > - unsigned int allocated; > }; > > struct privcmd_buf_vma_private { > @@ -60,13 +54,10 @@ static void privcmd_buf_vmapriv_free(struct privcmd_buf_vma_private *vma_priv) > { > unsigned int i; > > - vma_priv->file_priv->allocated -= vma_priv->n_pages; > - > list_del(&vma_priv->list); > > for (i = 0; i < vma_priv->n_pages; i++) > - if (vma_priv->pages[i]) > - __free_page(vma_priv->pages[i]); > + __free_page(vma_priv->pages[i]); > > kfree(vma_priv); > } > @@ -146,8 +137,7 @@ static int privcmd_buf_mmap(struct file *file, struct vm_area_struct *vma) > unsigned int i; > int ret = 0; > > - if (!(vma->vm_flags & VM_SHARED) || count > limit || > - file_priv->allocated + count > limit) > + if (!(vma->vm_flags & VM_SHARED)) > return -EINVAL; > > vma_priv = kzalloc(sizeof(*vma_priv) + count * sizeof(void *), > @@ -155,19 +145,15 @@ static int privcmd_buf_mmap(struct file *file, struct vm_area_struct *vma) > if (!vma_priv) > return -ENOMEM; > > - vma_priv->n_pages = count; > - count = 0; > - for (i = 0; i < vma_priv->n_pages; i++) { > + for (i = 0; i < count; i++) { > vma_priv->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO); > if (!vma_priv->pages[i]) > break; > - count++; > + vma_priv->n_pages++; > } > > mutex_lock(&file_priv->lock); > > - file_priv->allocated += count; > - > vma_priv->file_priv = file_priv; > vma_priv->users = 1; > >