From patchwork Thu Sep 10 12:21:01 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oliver Neukum X-Patchwork-Id: 258580 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=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, 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 65884C43461 for ; Thu, 10 Sep 2020 12:25:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2A13F20C09 for ; Thu, 10 Sep 2020 12:25:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730477AbgIJMYt (ORCPT ); Thu, 10 Sep 2020 08:24:49 -0400 Received: from mx2.suse.de ([195.135.220.15]:53638 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730508AbgIJMVb (ORCPT ); Thu, 10 Sep 2020 08:21:31 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 65F6EAFF6; Thu, 10 Sep 2020 12:21:33 +0000 (UTC) From: Oliver Neukum To: penguin-kernel@i-love.sakura.ne.jp, bjorn@mork.no, linux-usb@vger.kernel.org Cc: Oliver Neukum Subject: [RFC 2/6] CDC-WDM: introduce a timeout in flush() Date: Thu, 10 Sep 2020 14:21:01 +0200 Message-Id: <20200910122105.13398-2-oneukum@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20200910122105.13398-1-oneukum@suse.com> References: <20200910122105.13398-1-oneukum@suse.com> Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Malicious or defective hardware may cease communication while flush() is running. In last consequence we need a timeout, as hardware that remains silent must be ignored. The 30 seconds are coming out of thin air. Reported-by: Tetsuo Handa Signed-off-by: Oliver Neukum --- drivers/usb/class/cdc-wdm.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c index adb3fc307083..fef011dc8dc4 100644 --- a/drivers/usb/class/cdc-wdm.c +++ b/drivers/usb/class/cdc-wdm.c @@ -58,6 +58,9 @@ MODULE_DEVICE_TABLE (usb, wdm_ids); #define WDM_MAX 16 +/* flush() is uninterruptible, but we cannot wait forever */ +#define WDM_FLUSH_TIMEOUT (30 * HZ) + /* CDC-WMC r1.1 requires wMaxCommand to be "at least 256 decimal (0x100)" */ #define WDM_DEFAULT_BUFSIZE 256 @@ -589,7 +592,7 @@ static int wdm_flush(struct file *file, fl_owner_t id) struct wdm_device *desc = file->private_data; int rv; - wait_event(desc->wait, + rv = wait_event_timeout(desc->wait, /* * needs both flags. We cannot do with one * because resetting it would cause a race @@ -597,11 +600,15 @@ static int wdm_flush(struct file *file, fl_owner_t id) * a disconnect */ !test_bit(WDM_IN_USE, &desc->flags) || - test_bit(WDM_DISCONNECTING, &desc->flags)); + test_bit(WDM_DISCONNECTING, &desc->flags), + WDM_FLUSH_TIMEOUT); /* cannot dereference desc->intf if WDM_DISCONNECTING */ if (test_bit(WDM_DISCONNECTING, &desc->flags)) return -ENODEV; + if (!rv) + return -EIO; + rv = desc->werr; if (rv < 0) dev_err(&desc->intf->dev, "Error in flush path: %d\n", @@ -662,6 +669,8 @@ static int wdm_open(struct inode *inode, struct file *file) /* using write lock to protect desc->count */ mutex_lock(&desc->wlock); if (!desc->count++) { + /* in case flush() had timed out */ + usb_kill_urb(desc->command); desc->werr = 0; desc->rerr = 0; rv = usb_submit_urb(desc->validity, GFP_KERNEL);