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=-18.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 B86A1C433E6 for ; Tue, 9 Mar 2021 13:24:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 720566521A for ; Tue, 9 Mar 2021 13:24:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230397AbhCINXf (ORCPT ); Tue, 9 Mar 2021 08:23:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:46970 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231197AbhCINXc (ORCPT ); Tue, 9 Mar 2021 08:23:32 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0A85364D8F; Tue, 9 Mar 2021 13:23:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1615296211; bh=n12bipCoY+Ve78fsW2Lqczd+xn9K8iT4eJ9QR01boN4=; h=Subject:To:From:Date:From; b=lqyHEH8d9QRb1GT+P5e8GTT6LKMYnGvRo/imRSw8dEf7rrjkzgS3BRr2qgLdpjerj Ayjc9AKpMYrilUk2McQ5vXYr/I9fHjyhPcTA43SW42me8TpuRNcJa2AupFFjT7nEJq KXvt9OHXvDRR/K0eMccV+oU4drTBIsUlgEUvbFT8= Subject: patch "USB: usblp: fix a hang in poll() if disconnected" added to usb-linus To: zaitcev@redhat.com, gregkh@linuxfoundation.org, qiang.zhang@windriver.com, stable@vger.kernel.org From: Date: Tue, 09 Mar 2021 14:23:28 +0100 Message-ID: <161529620899115@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org This is a note to let you know that I've just added the patch titled USB: usblp: fix a hang in poll() if disconnected to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will hopefully also be merged in Linus's tree for the next -rc kernel release. If you have any questions about this process, please let me know. >From 623fe7c4e20f89b462c595b81d28ac208cfeeb11 Mon Sep 17 00:00:00 2001 From: Pete Zaitcev Date: Wed, 3 Mar 2021 22:10:53 -0600 Subject: USB: usblp: fix a hang in poll() if disconnected Apparently an application that opens a device and calls select() on it, will hang if the decice is disconnected. It's a little surprising that we had this bug for 15 years, but apparently nobody ever uses select() with a printer: only write() and read(), and those work fine. Well, you can also select() with a timeout. The fix is modeled after devio.c. A few other drivers check the condition first, then do not add the wait queue in case the device is disconnected. We doubt that's completely race-free. So, this patch adds the process first, then locks properly and checks for the disconnect. Reviewed-by: Zqiang Signed-off-by: Pete Zaitcev Cc: stable Link: https://lore.kernel.org/r/20210303221053.1cf3313e@suzdal.zaitcev.lan Signed-off-by: Greg Kroah-Hartman --- drivers/usb/class/usblp.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c index c9f6e9758288..f27b4aecff3d 100644 --- a/drivers/usb/class/usblp.c +++ b/drivers/usb/class/usblp.c @@ -494,16 +494,24 @@ static int usblp_release(struct inode *inode, struct file *file) /* No kernel lock - fine */ static __poll_t usblp_poll(struct file *file, struct poll_table_struct *wait) { - __poll_t ret; + struct usblp *usblp = file->private_data; + __poll_t ret = 0; unsigned long flags; - struct usblp *usblp = file->private_data; /* Should we check file->f_mode & FMODE_WRITE before poll_wait()? */ poll_wait(file, &usblp->rwait, wait); poll_wait(file, &usblp->wwait, wait); + + mutex_lock(&usblp->mut); + if (!usblp->present) + ret |= EPOLLHUP; + mutex_unlock(&usblp->mut); + spin_lock_irqsave(&usblp->lock, flags); - ret = ((usblp->bidir && usblp->rcomplete) ? EPOLLIN | EPOLLRDNORM : 0) | - ((usblp->no_paper || usblp->wcomplete) ? EPOLLOUT | EPOLLWRNORM : 0); + if (usblp->bidir && usblp->rcomplete) + ret |= EPOLLIN | EPOLLRDNORM; + if (usblp->no_paper || usblp->wcomplete) + ret |= EPOLLOUT | EPOLLWRNORM; spin_unlock_irqrestore(&usblp->lock, flags); return ret; } -- 2.30.1