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=-6.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 2735CC07E85 for ; Tue, 11 Dec 2018 16:00:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DF0CD2086D for ; Tue, 11 Dec 2018 16:00:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1544544003; bh=3Z0DO6kWqrWlEhMdNbbaK7Jvsbp9eqZMqcbj5GhHxPk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=VIeSfQ2BrOOWczth3lkBZxZRulCw9GbSXTeXQD+m/5AFIZoSNaJyScjvm1E2JuxqW AXo9Q8A36aBri48onidewtI/0rVLEkuC4VNTDWCphUKX2B13J43czKyRpH3EIyx4C0 j90DSNsq6NbO1Ne/vGeKZEJtT74bSd5+JUL40SuY= DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DF0CD2086D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730849AbeLKQAB (ORCPT ); Tue, 11 Dec 2018 11:00:01 -0500 Received: from mail.kernel.org ([198.145.29.99]:48116 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730381AbeLKP6g (ORCPT ); Tue, 11 Dec 2018 10:58:36 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.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 C320E20855; Tue, 11 Dec 2018 15:58:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1544543915; bh=3Z0DO6kWqrWlEhMdNbbaK7Jvsbp9eqZMqcbj5GhHxPk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LtgDA+mFP/KcxOT8Lj9bq0Te1A950XtRYfL8JimmCLZGVCSIB1kPh0ib/2h3ykxbl HwaIBqbCnwui7nUmnywE0sOGzfG+0uaW8VAw79l7AUE399iA7od3HOOJtcoD0MuRg8 IiBEV+uN2EMgDB6CqsYbX1lmlbFp3gv6dmmo9/2U= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Halil Pasic , Colin Ian King , Cornelia Huck , "Michael S. Tsirkin" Subject: [PATCH 4.19 078/118] virtio/s390: fix race in ccw_io_helper() Date: Tue, 11 Dec 2018 16:41:37 +0100 Message-Id: <20181211151647.412003042@linuxfoundation.org> X-Mailer: git-send-email 2.20.0 In-Reply-To: <20181211151644.216668863@linuxfoundation.org> References: <20181211151644.216668863@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore 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 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Halil Pasic commit 78b1a52e05c9db11d293342e8d6d8a230a04b4e7 upstream. While ccw_io_helper() seems like intended to be exclusive in a sense that it is supposed to facilitate I/O for at most one thread at any given time, there is actually nothing ensuring that threads won't pile up at vcdev->wait_q. If they do, all threads get woken up and see the status that belongs to some other request than their own. This can lead to bugs. For an example see: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1788432 This race normally does not cause any problems. The operations provided by struct virtio_config_ops are usually invoked in a well defined sequence, normally don't fail, and are normally used quite infrequent too. Yet, if some of the these operations are directly triggered via sysfs attributes, like in the case described by the referenced bug, userspace is given an opportunity to force races by increasing the frequency of the given operations. Let us fix the problem by ensuring, that for each device, we finish processing the previous request before starting with a new one. Signed-off-by: Halil Pasic Reported-by: Colin Ian King Cc: stable@vger.kernel.org Message-Id: <20180925121309.58524-3-pasic@linux.ibm.com> Signed-off-by: Cornelia Huck Signed-off-by: Michael S. Tsirkin Signed-off-by: Greg Kroah-Hartman --- drivers/s390/virtio/virtio_ccw.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/drivers/s390/virtio/virtio_ccw.c +++ b/drivers/s390/virtio/virtio_ccw.c @@ -56,6 +56,7 @@ struct virtio_ccw_device { unsigned int revision; /* Transport revision */ wait_queue_head_t wait_q; spinlock_t lock; + struct mutex io_lock; /* Serializes I/O requests */ struct list_head virtqueues; unsigned long indicators; unsigned long indicators2; @@ -296,6 +297,7 @@ static int ccw_io_helper(struct virtio_c unsigned long flags; int flag = intparm & VIRTIO_CCW_INTPARM_MASK; + mutex_lock(&vcdev->io_lock); do { spin_lock_irqsave(get_ccwdev_lock(vcdev->cdev), flags); ret = ccw_device_start(vcdev->cdev, ccw, intparm, 0, 0); @@ -308,7 +310,9 @@ static int ccw_io_helper(struct virtio_c cpu_relax(); } while (ret == -EBUSY); wait_event(vcdev->wait_q, doing_io(vcdev, flag) == 0); - return ret ? ret : vcdev->err; + ret = ret ? ret : vcdev->err; + mutex_unlock(&vcdev->io_lock); + return ret; } static void virtio_ccw_drop_indicator(struct virtio_ccw_device *vcdev, @@ -1253,6 +1257,7 @@ static int virtio_ccw_online(struct ccw_ init_waitqueue_head(&vcdev->wait_q); INIT_LIST_HEAD(&vcdev->virtqueues); spin_lock_init(&vcdev->lock); + mutex_init(&vcdev->io_lock); spin_lock_irqsave(get_ccwdev_lock(cdev), flags); dev_set_drvdata(&cdev->dev, vcdev);