From patchwork Thu Dec 12 12:37:23 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paul Durrant X-Patchwork-Id: 11288035 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 13A0C13B6 for ; Thu, 12 Dec 2019 12:39:01 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E418E21655 for ; Thu, 12 Dec 2019 12:39:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="ZOXWWasn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E418E21655 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=amazon.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1ifNj8-00088F-IU; Thu, 12 Dec 2019 12:37:54 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1ifNj6-000885-Mn for xen-devel@lists.xenproject.org; Thu, 12 Dec 2019 12:37:52 +0000 X-Inumbo-ID: 36417d6c-1cdc-11ea-b6f1-bc764e2007e4 Received: from smtp-fw-9101.amazon.com (unknown [207.171.184.25]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 36417d6c-1cdc-11ea-b6f1-bc764e2007e4; Thu, 12 Dec 2019 12:37:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1576154273; x=1607690273; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=64i9dOS4nNgwTFfSAmSWV7jMZ71ZQlmzTwYxEKBpjQc=; b=ZOXWWasnhBVeZxq7O0dUAJJ/VdHQEynkqNuDL+tL52AoxlOvxkIyQ5YO Fvo4nGHQMN+oW0v3voIDZW4H9jYRTe0RIV0DV7d76/9T7AjT+sebE35RK r2ey9TD4yaLjPgldkSmOruYAI4ZUj3OIxanSIb+VYwcswDHBsmQCPCI62 4=; 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: , , 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 Precedence: Bulk Subject: [Xen-devel] [PATCH net] xen-netback: avoid race that can lead to NULL pointer dereference X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Juergen Gross , Paul Durrant , Jakub Kicinski , Wei Liu , "David S. Miller" Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" 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 Acked-by: Wei Liu --- 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); }