From patchwork Wed Aug 12 13:20:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oliver Neukum X-Patchwork-Id: 11710813 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 053B51392 for ; Wed, 12 Aug 2020 13:20:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E16FD207DA for ; Wed, 12 Aug 2020 13:20:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728012AbgHLNUu (ORCPT ); Wed, 12 Aug 2020 09:20:50 -0400 Received: from mx2.suse.de ([195.135.220.15]:55714 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727817AbgHLNUs (ORCPT ); Wed, 12 Aug 2020 09:20:48 -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 02DCEB76B; Wed, 12 Aug 2020 13:21:09 +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 2/5] CDC-WDM: introduce a timeout in flush() Date: Wed, 12 Aug 2020 15:20:31 +0200 Message-Id: <20200812132034.14363-3-oneukum@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20200812132034.14363-1-oneukum@suse.com> References: <20200812132034.14363-1-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 | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c index a834294ce4e5..329f8d5f7c8d 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 +600,14 @@ 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", @@ -659,6 +665,14 @@ static int wdm_open(struct inode *inode, struct file *file) goto out; } + /* + * in case flush() had timed out + */ + usb_kill_urb(desc->command); + spin_lock_irq(&desc->iuspin); + desc->werr = 0; + spin_unlock_irq(&desc->iuspin); + /* using write lock to protect desc->count */ mutex_lock(&desc->wlock); if (!desc->count++) {