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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 39F66C3436D for ; Fri, 13 Dec 2019 20:37:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 63A7224751 for ; Fri, 13 Dec 2019 20:37:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="q+yFsIPL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727261AbfLMNUv (ORCPT ); Fri, 13 Dec 2019 08:20:51 -0500 Received: from smtp-fw-6002.amazon.com ([52.95.49.90]:41412 "EHLO smtp-fw-6002.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726386AbfLMNUv (ORCPT ); Fri, 13 Dec 2019 08:20:51 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1576243250; x=1607779250; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=tFySCLGtPwSbxUYEux7/p0Qq1N3sbGfPAhYwtPWA8rI=; b=q+yFsIPL9vjV7Vk8SVEayXkaH+KzTUeReqwRvOFeNS/hB2HWIKZ12k1U iu1yQG7MkOIFrMQmSTlWEqsHAO+ihcF6cijHLC6QLcfTd/1Vwp1+M4jEv VNUV/SMdSTB+K8S1R80jvVX4TjM1kzeXAU1RpYgXxqdNuDQTsAqkXCaD/ 8=; IronPort-SDR: O0jhjvelAXfwKAOT+PVxdrI3ucPHYGBWbSCbkKO9chIdq5QSf3fZxfvnAusUejisOvPnXz7Kg1 G9cNGYjF/sKQ== X-IronPort-AV: E=Sophos;i="5.69,309,1571702400"; d="scan'208";a="7497894" Received: from iad6-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-1e-27fb8269.us-east-1.amazon.com) ([10.124.125.6]) by smtp-border-fw-out-6002.iad6.amazon.com with ESMTP; 13 Dec 2019 13:20:49 +0000 Received: from EX13MTAUEA001.ant.amazon.com (iad55-ws-svc-p15-lb9-vlan3.iad.amazon.com [10.40.159.166]) by email-inbound-relay-1e-27fb8269.us-east-1.amazon.com (Postfix) with ESMTPS id 181C5A1B8E; Fri, 13 Dec 2019 13:20:47 +0000 (UTC) Received: from EX13D32EUB002.ant.amazon.com (10.43.166.114) by EX13MTAUEA001.ant.amazon.com (10.43.61.243) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Fri, 13 Dec 2019 13:20:46 +0000 Received: from EX13MTAUWA001.ant.amazon.com (10.43.160.58) by EX13D32EUB002.ant.amazon.com (10.43.166.114) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Fri, 13 Dec 2019 13:20:45 +0000 Received: from u2f063a87eabd5f.cbg10.amazon.com (10.125.106.135) by mail-relay.amazon.com (10.43.160.118) with Microsoft SMTP Server id 15.0.1367.3 via Frontend Transport; Fri, 13 Dec 2019 13:20:43 +0000 From: Paul Durrant To: , , CC: Paul Durrant , Juergen Gross , "Jakub Kicinski" , Wei Liu , "David S. Miller" Subject: [PATCH net v2] xen-netback: avoid race that can lead to NULL pointer dereference Date: Fri, 13 Dec 2019 13:20:40 +0000 Message-ID: <20191213132040.21446-1-pdurrant@amazon.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org In function xenvif_disconnect_queue(), the value of queue->rx_irq is zeroed *before* queue->task is stopped. Unfortunately that task may call notify_remote_via_irq(queue->rx_irq) and calling that function with a zero value results in a NULL pointer dereference in evtchn_from_irq(). This patch simply re-orders things, stopping all tasks before zero-ing the irq values, thereby avoiding the possibility of the race. Fixes: 2ac061ce97f4 ("xen/netback: cleanup init and deinit code") Signed-off-by: Paul Durrant --- Cc: Juergen Gross Cc: Jakub Kicinski Cc: Wei Liu Cc: "David S. Miller" v2: - Add 'Fixes' tag and re-work commit comment --- drivers/net/xen-netback/interface.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c index 68dd7bb07ca6..f15ba3de6195 100644 --- a/drivers/net/xen-netback/interface.c +++ b/drivers/net/xen-netback/interface.c @@ -628,18 +628,6 @@ int xenvif_connect_ctrl(struct xenvif *vif, grant_ref_t ring_ref, static void xenvif_disconnect_queue(struct xenvif_queue *queue) { - if (queue->tx_irq) { - unbind_from_irqhandler(queue->tx_irq, queue); - if (queue->tx_irq == queue->rx_irq) - queue->rx_irq = 0; - queue->tx_irq = 0; - } - - if (queue->rx_irq) { - unbind_from_irqhandler(queue->rx_irq, queue); - queue->rx_irq = 0; - } - if (queue->task) { kthread_stop(queue->task); queue->task = NULL; @@ -655,6 +643,18 @@ static void xenvif_disconnect_queue(struct xenvif_queue *queue) queue->napi.poll = NULL; } + if (queue->tx_irq) { + unbind_from_irqhandler(queue->tx_irq, queue); + if (queue->tx_irq == queue->rx_irq) + queue->rx_irq = 0; + queue->tx_irq = 0; + } + + if (queue->rx_irq) { + unbind_from_irqhandler(queue->rx_irq, queue); + queue->rx_irq = 0; + } + xenvif_unmap_frontend_data_rings(queue); } -- 2.20.1