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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 15A2CC4CEC4 for ; Thu, 19 Sep 2019 22:21:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D9404217D6 for ; Thu, 19 Sep 2019 22:21:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568931684; bh=A7T8CFDm/h4B79sB4NYCgtnTg1DZ0ENRpvKZ03VCHAc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ASYRyZCtMpOcqQbVnkXkVhcjBtRgwOXe6CjdoT5FypX76Iv/0fLx9gISyndHRroDF TjAZ6RZCsQIydW/WWf4blvh7qYyaxm2QO3rggQNIjDgTTmZwTdLoRTG6OnebCFFDpD HhuE1OMpct561UfuOZ0coJO4Ik/7A1Ltj2PiBmcg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406729AbfISWVY (ORCPT ); Thu, 19 Sep 2019 18:21:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:35816 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406712AbfISWVV (ORCPT ); Thu, 19 Sep 2019 18:21:21 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AAEAF21924; Thu, 19 Sep 2019 22:21:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568931681; bh=A7T8CFDm/h4B79sB4NYCgtnTg1DZ0ENRpvKZ03VCHAc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sz4F2ABUZ8qWaXeS96QeXf943jbqShfSPZOH2J+PWofB9ySNDlQNJjqlyHBM/yxNV x2BgY5NKOTpp/CsHaT3r5T9xPJAlJfyqruWE2i0ovACYZZjLUlSj0aBhW3dnwlhDt5 S10Q6MGHiBtreseBgvIg5dxVCabuXMbY1KK5qAI8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dongli Zhang , "David S. Miller" Subject: [PATCH 4.9 39/74] xen-netfront: do not assume sk_buff_head list is empty in error handling Date: Fri, 20 Sep 2019 00:03:52 +0200 Message-Id: <20190919214808.712612375@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190919214800.519074117@linuxfoundation.org> References: <20190919214800.519074117@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dongli Zhang [ Upstream commit 00b368502d18f790ab715e055869fd4bb7484a9b ] When skb_shinfo(skb) is not able to cache extra fragment (that is, skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS), xennet_fill_frags() assumes the sk_buff_head list is already empty. As a result, cons is increased only by 1 and returns to error handling path in xennet_poll(). However, if the sk_buff_head list is not empty, queue->rx.rsp_cons may be set incorrectly. That is, queue->rx.rsp_cons would point to the rx ring buffer entries whose queue->rx_skbs[i] and queue->grant_rx_ref[i] are already cleared to NULL. This leads to NULL pointer access in the next iteration to process rx ring buffer entries. Below is how xennet_poll() does error handling. All remaining entries in tmpq are accounted to queue->rx.rsp_cons without assuming how many outstanding skbs are remained in the list. 985 static int xennet_poll(struct napi_struct *napi, int budget) ... ... 1032 if (unlikely(xennet_set_skb_gso(skb, gso))) { 1033 __skb_queue_head(&tmpq, skb); 1034 queue->rx.rsp_cons += skb_queue_len(&tmpq); 1035 goto err; 1036 } It is better to always have the error handling in the same way. Fixes: ad4f15dc2c70 ("xen/netfront: don't bug in case of too many frags") Signed-off-by: Dongli Zhang Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/xen-netfront.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -907,7 +907,7 @@ static RING_IDX xennet_fill_frags(struct __pskb_pull_tail(skb, pull_to - skb_headlen(skb)); } if (unlikely(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS)) { - queue->rx.rsp_cons = ++cons; + queue->rx.rsp_cons = ++cons + skb_queue_len(list); kfree_skb(nskb); return ~0U; }