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=-12.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,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 B9130C43219 for ; Mon, 29 Apr 2019 14:19:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8A42F20675 for ; Mon, 29 Apr 2019 14:19:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556547598; bh=VKVaiJyL+JKM11ViNlbHc4QIv4y3EhoeerhacuYWGuc=; h=Subject:To:From:Date:List-ID:From; b=o8h0mPsTpB7qtz+uJvK1Lud7mIRfg+hpJSBY7UnNvMzrBmXaBuHp3C1lERx3gIszh ATrXcfP2DZnus0hK3c8nl8k8Wl3u5EzzvGeY4vb7p74OvNUREOsP00W26F1BvD3qAQ 9YBe8s2CA017zbCmx9TJMEZkBzbPCl6q1OG5rvP0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728258AbfD2OT6 (ORCPT ); Mon, 29 Apr 2019 10:19:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:37032 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728253AbfD2OT6 (ORCPT ); Mon, 29 Apr 2019 10:19:58 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.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 08A6D20673; Mon, 29 Apr 2019 14:19:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556547596; bh=VKVaiJyL+JKM11ViNlbHc4QIv4y3EhoeerhacuYWGuc=; h=Subject:To:From:Date:From; b=gfwg+5wn1+gYOG41KUecHVYwR80uWNMG3gLFYW88cLPxfaZjMd6VKcr2ziMB3cmyW NVxuc2dB7xiM03hn34pNfIGtmPs5eZyxFHm8F/Rlyk0H9gbMDy1HQ65O3Yclyjwu9W WyK63/30Ak8Z3LYmUczT9I6LPI5XaELHXp0AvOoo= Subject: patch "USB: cdc-acm: fix unthrottle races" added to usb-testing To: johan@kernel.org, gregkh@linuxfoundation.org, oneukum@suse.com, stable@vger.kernel.org From: Date: Mon, 29 Apr 2019 16:19:54 +0200 Message-ID: <15565475945724@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org 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: cdc-acm: fix unthrottle races 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-testing 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 be merged to the usb-next branch sometime soon, after it passes testing, and the merge window is open. If you have any questions about this process, please let me know. >From 764478f41130f1b8d8057575b89e69980a0f600d Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Thu, 25 Apr 2019 18:05:39 +0200 Subject: USB: cdc-acm: fix unthrottle races Fix two long-standing bugs which could potentially lead to memory corruption or leave the port throttled until it is reopened (on weakly ordered systems), respectively, when read-URB completion races with unthrottle(). First, the URB must not be marked as free before processing is complete to prevent it from being submitted by unthrottle() on another CPU. CPU 1 CPU 2 ================ ================ complete() unthrottle() process_urb(); smp_mb__before_atomic(); set_bit(i, free); if (test_and_clear_bit(i, free)) submit_urb(); Second, the URB must be marked as free before checking the throttled flag to prevent unthrottle() on another CPU from failing to observe that the URB needs to be submitted if complete() sees that the throttled flag is set. CPU 1 CPU 2 ================ ================ complete() unthrottle() set_bit(i, free); throttled = 0; smp_mb__after_atomic(); smp_mb(); if (throttled) if (test_and_clear_bit(i, free)) return; submit_urb(); Note that test_and_clear_bit() only implies barriers when the test is successful. To handle the case where the URB is still in use an explicit barrier needs to be added to unthrottle() for the second race condition. Also note that the first race was fixed by 36e59e0d70d6 ("cdc-acm: fix race between callback and unthrottle") back in 2015, but the bug was reintroduced a year later. Fixes: 1aba579f3cf5 ("cdc-acm: handle read pipe errors") Fixes: 088c64f81284 ("USB: cdc-acm: re-write read processing") Signed-off-by: Johan Hovold Acked-by: Oliver Neukum Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/usb/class/cdc-acm.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index ec666eb4b7b4..c03aa8550980 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -470,12 +470,12 @@ static void acm_read_bulk_callback(struct urb *urb) struct acm *acm = rb->instance; unsigned long flags; int status = urb->status; + bool stopped = false; + bool stalled = false; dev_vdbg(&acm->data->dev, "got urb %d, len %d, status %d\n", rb->index, urb->actual_length, status); - set_bit(rb->index, &acm->read_urbs_free); - if (!acm->dev) { dev_dbg(&acm->data->dev, "%s - disconnected\n", __func__); return; @@ -488,15 +488,16 @@ static void acm_read_bulk_callback(struct urb *urb) break; case -EPIPE: set_bit(EVENT_RX_STALL, &acm->flags); - schedule_work(&acm->work); - return; + stalled = true; + break; case -ENOENT: case -ECONNRESET: case -ESHUTDOWN: dev_dbg(&acm->data->dev, "%s - urb shutting down with status: %d\n", __func__, status); - return; + stopped = true; + break; default: dev_dbg(&acm->data->dev, "%s - nonzero urb status received: %d\n", @@ -505,10 +506,24 @@ static void acm_read_bulk_callback(struct urb *urb) } /* - * Unthrottle may run on another CPU which needs to see events - * in the same order. Submission has an implict barrier + * Make sure URB processing is done before marking as free to avoid + * racing with unthrottle() on another CPU. Matches the barriers + * implied by the test_and_clear_bit() in acm_submit_read_urb(). */ smp_mb__before_atomic(); + set_bit(rb->index, &acm->read_urbs_free); + /* + * Make sure URB is marked as free before checking the throttled flag + * to avoid racing with unthrottle() on another CPU. Matches the + * smp_mb() in unthrottle(). + */ + smp_mb__after_atomic(); + + if (stopped || stalled) { + if (stalled) + schedule_work(&acm->work); + return; + } /* throttle device if requested by tty */ spin_lock_irqsave(&acm->read_lock, flags); @@ -842,6 +857,9 @@ static void acm_tty_unthrottle(struct tty_struct *tty) acm->throttle_req = 0; spin_unlock_irq(&acm->read_lock); + /* Matches the smp_mb__after_atomic() in acm_read_bulk_callback(). */ + smp_mb(); + if (was_throttled) acm_submit_read_urbs(acm, GFP_KERNEL); } -- 2.21.0