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=-9.9 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,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 8DB1EC00454 for ; Thu, 12 Dec 2019 12:37:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 63C9322B48 for ; Thu, 12 Dec 2019 12:37:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="YwBVWriE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729287AbfLLMhx (ORCPT ); Thu, 12 Dec 2019 07:37:53 -0500 Received: from smtp-fw-9101.amazon.com ([207.171.184.25]:1778 "EHLO smtp-fw-9101.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729157AbfLLMhw (ORCPT ); Thu, 12 Dec 2019 07:37:52 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1576154272; x=1607690272; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=64i9dOS4nNgwTFfSAmSWV7jMZ71ZQlmzTwYxEKBpjQc=; b=YwBVWriEPo3H0XaPTyAZBKR5NqaZK4T5A778guGAwvIIbgmeZDPG2Zjf FWdHsZnMt0ZH5OhMXwuUEkLnRKErl7wIWfbWGzpiEGbke3qLO5nQ2HtTt vPafJLhUZ8I6k+GjL69v7M26/7zPVtfbUMf/v+jFpdgWelJdNTMRD2VMY g=; IronPort-SDR: u48cjDvfsDaqvN8mi03+dtkm+PjjjAcd0TOEvApWEU4rNGoaDFBQwhsWz1lW0OSTr6EgStUtWO qWR9JC3DsDjA== X-IronPort-AV: E=Sophos;i="5.69,305,1571702400"; d="scan'208";a="4722440" Received: from sea32-co-svc-lb4-vlan3.sea.corp.amazon.com (HELO email-inbound-relay-1e-97fdccfd.us-east-1.amazon.com) ([10.47.23.38]) by smtp-border-fw-out-9101.sea19.amazon.com with ESMTP; 12 Dec 2019 12:37:39 +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-97fdccfd.us-east-1.amazon.com (Postfix) with ESMTPS id B8FDBA1CBF; Thu, 12 Dec 2019 12:37:36 +0000 (UTC) Received: from EX13D32EUB004.ant.amazon.com (10.43.166.212) by EX13MTAUEA001.ant.amazon.com (10.43.61.243) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Thu, 12 Dec 2019 12:37:36 +0000 Received: from EX13MTAUWA001.ant.amazon.com (10.43.160.58) by EX13D32EUB004.ant.amazon.com (10.43.166.212) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Thu, 12 Dec 2019 12:37:35 +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; Thu, 12 Dec 2019 12:37:32 +0000 From: Paul Durrant To: , , CC: Paul Durrant , Juergen Gross , "Jakub Kicinski" , Wei Liu , "David S. Miller" Subject: [PATCH net] xen-netback: avoid race that can lead to NULL pointer dereference Date: Thu, 12 Dec 2019 12:37:23 +0000 Message-ID: <20191212123723.21548-1-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 Commit 2ac061ce97f4 ("xen/netback: cleanup init and deinit code") introduced a problem. 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. Signed-off-by: Paul Durrant --- Cc: Juergen Gross Cc: Jakub Kicinski Cc: Wei Liu Cc: "David S. Miller" --- 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