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=-3.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 489A2C07E85 for ; Sun, 9 Dec 2018 22:09:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1804420661 for ; Sun, 9 Dec 2018 22:09:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1804420661 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=decadent.org.uk 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 S1727713AbeLIWJX (ORCPT ); Sun, 9 Dec 2018 17:09:23 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:37422 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727045AbeLIWJS (ORCPT ); Sun, 9 Dec 2018 17:09:18 -0500 Received: from pub.yeoldevic.com ([81.174.156.145] helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1gW73F-0002pp-Li; Sun, 09 Dec 2018 21:55:49 +0000 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1gW72d-0003NT-49; Sun, 09 Dec 2018 21:55:11 +0000 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Dominique Martinet" , "Chirantan Ekbote" , "Dylan Reid" , "Guenter Roeck" , "Greg Kurz" Date: Sun, 09 Dec 2018 21:50:33 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 128/328] 9p/net: Fix zero-copy path in the 9p virtio transport In-Reply-To: X-SA-Exim-Connect-IP: 81.174.156.145 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.62-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Chirantan Ekbote commit d28c756caee6e414d9ba367d0b92da24145af2a8 upstream. The zero-copy optimization when reading or writing large chunks of data is quite useful. However, the 9p messages created through the zero-copy write path have an incorrect message size: it should be the size of the header + size of the data being written but instead it's just the size of the header. This only works if the server ignores the size field of the message and otherwise breaks the framing of the protocol. Fix this by re-writing the message size field with the correct value. Tested by running `dd if=/dev/zero of=out bs=4k count=1` inside a virtio-9p mount. Link: http://lkml.kernel.org/r/20180717003529.114368-1-chirantan@chromium.org Signed-off-by: Chirantan Ekbote Reviewed-by: Greg Kurz Tested-by: Greg Kurz Cc: Dylan Reid Cc: Guenter Roeck Signed-off-by: Dominique Martinet [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- net/9p/trans_virtio.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/net/9p/trans_virtio.c +++ b/net/9p/trans_virtio.c @@ -378,6 +378,7 @@ p9_virtio_zc_request(struct p9_client *c p9_debug(P9_DEBUG_TRANS, "virtio request\n"); if (uodata) { + __le32 sz; out_nr_pages = p9_nr_pages(uodata, outlen); out_pages = kmalloc(sizeof(struct page *) * out_nr_pages, GFP_NOFS); @@ -393,6 +394,12 @@ p9_virtio_zc_request(struct p9_client *c out_pages = NULL; goto err_out; } + /* The size field of the message must include the length of the + * header and the length of the data. We didn't actually know + * the length of the data until this point so add it in now. + */ + sz = cpu_to_le32(req->tc->size + outlen); + memcpy(&req->tc->sdata[0], &sz, sizeof(sz)); } if (uidata) { in_nr_pages = p9_nr_pages(uidata, inlen);