From patchwork Thu Jan 21 15:30:45 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oliver Neukum X-Patchwork-Id: 368407 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED 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 CE0D0C433E0 for ; Thu, 21 Jan 2021 15:31:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8539E23A1C for ; Thu, 21 Jan 2021 15:31:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733029AbhAUPbr (ORCPT ); Thu, 21 Jan 2021 10:31:47 -0500 Received: from mx2.suse.de ([195.135.220.15]:49858 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733008AbhAUPbl (ORCPT ); Thu, 21 Jan 2021 10:31:41 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1611243047; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type; bh=j2qtzAuvduKZjvG5q6dUdqvbwQC8zhmdBkegcyXaqxY=; b=vQXOjO5SNBRtgT0bUXXVjrMduwdAUDv5wY0Qgk0gJ1dxf2Yq1cTKt22My6GU6uKgr/sUhr kd2ciJiAUhJCCTefFiLojrIb52jegnbkuThbiS2vVjWeyIVioYS9HvmZhgrMakUlpPs9g+ 2PmmbFQVnATCiRSkNtE1/ta3mfW9DEA= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 548A7B1D5; Thu, 21 Jan 2021 15:30:47 +0000 (UTC) Message-ID: <3dfe07c7ad08d4dfd7eac7bd54e6b821319abe90.camel@suse.com> Subject: circular submissions in cdc-wdm and how to break them on disconnect From: Oliver Neukum To: Tetsuo Handa Cc: linux-usb@vger.kernel.org Date: Thu, 21 Jan 2021 16:30:45 +0100 User-Agent: Evolution 3.34.4 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Hi, you have moved kill_urbs() below cancel_work_sync(&desc->rxwork); cancel_work_sync(&desc->service_outs_intr); to close a race, as rv = usb_submit_urb(desc->response, GFP_KERNEL); in service_outstanding_interrupt() would submit the response URB, right? Unfortunately we have in wdm_in_callback() the following code path if (desc->rerr) { /* * Since there was an error, userspace may decide to not read * any data after poll'ing. * We should respond to further attempts from the device to send * data, so that we can get unstuck. */ schedule_work(&desc->service_outs_intr); It looks to me like we have a circular dependency here and this needs some change to break. What do you think about the attached patch? Regards Oliver Signed-off-by: Oliver Neukum >From efdd52b67f24e4fa2552f8cc2cbedb7118f71291 Mon Sep 17 00:00:00 2001 From: Oliver Neukum Date: Mon, 4 Jan 2021 17:26:33 +0100 Subject: [PATCH] cdc-wdm: support for poisoning and unpoisoning the URBs We have a cycle of callbacks scheduling works which submit URBs. This needs to be broken. Signed-off-by: Oliver Neukum --- drivers/usb/class/cdc-wdm.c | 30 ++++++++++++++++++++++-------- 1 file changed, 22 insertions(+), 8 deletions(-) diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c index 508b1c3f8b73..d1e4a7379beb 100644 --- a/drivers/usb/class/cdc-wdm.c +++ b/drivers/usb/class/cdc-wdm.c @@ -321,12 +321,23 @@ static void wdm_int_callback(struct urb *urb) } -static void kill_urbs(struct wdm_device *desc) +static void poison_urbs(struct wdm_device *desc) { /* the order here is essential */ - usb_kill_urb(desc->command); - usb_kill_urb(desc->validity); - usb_kill_urb(desc->response); + usb_poison_urb(desc->command); + usb_poison_urb(desc->validity); + usb_poison_urb(desc->response); +} + +static void unpoison_urbs(struct wdm_device *desc) +{ + /* + * the order here is not essential + * it is symmetrical just to be nice + */ + usb_unpoison_urb(desc->response); + usb_unpoison_urb(desc->validity); + usb_unpoison_urb(desc->command); } static void free_urbs(struct wdm_device *desc) @@ -741,11 +752,12 @@ static int wdm_release(struct inode *inode, struct file *file) if (!desc->count) { if (!test_bit(WDM_DISCONNECTING, &desc->flags)) { dev_dbg(&desc->intf->dev, "wdm_release: cleanup\n"); - kill_urbs(desc); + poison_urbs(desc); spin_lock_irq(&desc->iuspin); desc->resp_count = 0; spin_unlock_irq(&desc->iuspin); desc->manage_power(desc->intf, 0); + unpoison_urbs(desc); } else { /* must avoid dev_printk here as desc->intf is invalid */ pr_debug(KBUILD_MODNAME " %s: device gone - cleaning up\n", __func__); @@ -1037,9 +1049,9 @@ static void wdm_disconnect(struct usb_interface *intf) wake_up_all(&desc->wait); mutex_lock(&desc->rlock); mutex_lock(&desc->wlock); + poison_urbs(desc); cancel_work_sync(&desc->rxwork); cancel_work_sync(&desc->service_outs_intr); - kill_urbs(desc); mutex_unlock(&desc->wlock); mutex_unlock(&desc->rlock); @@ -1080,9 +1092,10 @@ static int wdm_suspend(struct usb_interface *intf, pm_message_t message) set_bit(WDM_SUSPENDING, &desc->flags); spin_unlock_irq(&desc->iuspin); /* callback submits work - order is essential */ - kill_urbs(desc); + poison_urbs(desc); cancel_work_sync(&desc->rxwork); cancel_work_sync(&desc->service_outs_intr); + unpoison_urbs(desc); } if (!PMSG_IS_AUTO(message)) { mutex_unlock(&desc->wlock); @@ -1140,7 +1153,7 @@ static int wdm_pre_reset(struct usb_interface *intf) wake_up_all(&desc->wait); mutex_lock(&desc->rlock); mutex_lock(&desc->wlock); - kill_urbs(desc); + poison_urbs(desc); cancel_work_sync(&desc->rxwork); cancel_work_sync(&desc->service_outs_intr); return 0; @@ -1151,6 +1164,7 @@ static int wdm_post_reset(struct usb_interface *intf) struct wdm_device *desc = wdm_find_device(intf); int rv; + unpoison_urbs(desc); clear_bit(WDM_OVERFLOW, &desc->flags); clear_bit(WDM_RESETTING, &desc->flags); rv = recover_from_urb_loss(desc); -- 2.26.2