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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 13445C3A5A2 for ; Fri, 20 Sep 2019 14:33:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E9D512086A for ; Fri, 20 Sep 2019 14:33:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391460AbfITOdJ (ORCPT ); Fri, 20 Sep 2019 10:33:09 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:36420 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388259AbfITOZJ (ORCPT ); Fri, 20 Sep 2019 10:25:09 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1iBJqH-00051F-U6; Fri, 20 Sep 2019 15:25:02 +0100 Received: from ben by deadeye with local (Exim 4.92.1) (envelope-from ) id 1iBJqH-0007yD-62; Fri, 20 Sep 2019 15:25:01 +0100 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, Denis Kirjanov , "ruippan" , "Michael S. Tsirkin" , "yongduan" , "Tyler Hicks" , "Lidong Chen" Date: Fri, 20 Sep 2019 15:23:35 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 112/132] vhost: make sure log_num < in_num In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 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 3.16.74-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: yongduan commit 060423bfdee3f8bc6e2c1bac97de24d5415e2bc4 upstream. The code assumes log_num < in_num everywhere, and that is true as long as in_num is incremented by descriptor iov count, and log_num by 1. However this breaks if there's a zero sized descriptor. As a result, if a malicious guest creates a vring desc with desc.len = 0, it may cause the host kernel to crash by overflowing the log array. This bug can be triggered during the VM migration. There's no need to log when desc.len = 0, so just don't increment log_num in this case. Fixes: 3a4d5c94e959 ("vhost_net: a kernel-level virtio server") Reviewed-by: Lidong Chen Signed-off-by: ruippan Signed-off-by: yongduan Acked-by: Michael S. Tsirkin Reviewed-by: Tyler Hicks Signed-off-by: Michael S. Tsirkin [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- drivers/vhost/vhost.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1194,7 +1194,7 @@ static int get_indirect(struct vhost_vir /* If this is an input descriptor, increment that count. */ if (desc.flags & VRING_DESC_F_WRITE) { *in_num += ret; - if (unlikely(log)) { + if (unlikely(log && ret)) { log[*log_num].addr = desc.addr; log[*log_num].len = desc.len; ++*log_num; @@ -1317,7 +1317,7 @@ int vhost_get_vq_desc(struct vhost_virtq /* If this is an input descriptor, * increment that count. */ *in_num += ret; - if (unlikely(log)) { + if (unlikely(log && ret)) { log[*log_num].addr = desc.addr; log[*log_num].len = desc.len; ++*log_num;