Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DCE9C433F5 for ; Thu, 14 Oct 2021 14:58:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E91EE6120A for ; Thu, 14 Oct 2021 14:58:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232873AbhJNPAY (ORCPT ); Thu, 14 Oct 2021 11:00:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:45066 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232655AbhJNO7R (ORCPT ); Thu, 14 Oct 2021 10:59:17 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8500D60FDC; Thu, 14 Oct 2021 14:57:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1634223433; bh=h5fZ2JcFHVDYuuSWQK277ZDC4zEypoMm7tQVgzk7wZw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HUbl5Th6pO/rtPuLsFoM0RYiIzZkM1fgWLWNSPr0+tTZiepJ+gXP+O8fNXm6g/BX6 W61hsBLC/35aoO4AZ03mtJZ2TUBFxAxHzp5sU8tq8+ob5TKjy36z7KVlBrvY2YwGEM 4Meu2ulsfqp1YwDzJXsrHvtU0C6CuUr4+r+lTrzU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Oliver Neukum , Johan Hovold Subject: [PATCH 4.14 02/33] USB: cdc-acm: fix racy tty buffer accesses Date: Thu, 14 Oct 2021 16:53:34 +0200 Message-Id: <20211014145208.855023917@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20211014145208.775270267@linuxfoundation.org> References: <20211014145208.775270267@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Johan Hovold commit 65a205e6113506e69a503b61d97efec43fc10fd7 upstream. A recent change that started reporting break events to the line discipline caused the tty-buffer insertions to no longer be serialised by inserting events also from the completion handler for the interrupt endpoint. Completion calls for distinct endpoints are not guaranteed to be serialised. For example, in case a host-controller driver uses bottom-half completion, the interrupt and bulk-in completion handlers can end up running in parallel on two CPUs (high-and low-prio tasklets, respectively) thereby breaking the tty layer's single producer assumption. Fix this by holding the read lock also when inserting characters from the bulk endpoint. Fixes: 08dff274edda ("cdc-acm: fix BREAK rx code path adding necessary calls") Cc: stable@vger.kernel.org Acked-by: Oliver Neukum Signed-off-by: Johan Hovold Link: https://lore.kernel.org/r/20210929090937.7410-2-johan@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/usb/class/cdc-acm.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -486,11 +486,16 @@ static int acm_submit_read_urbs(struct a static void acm_process_read_urb(struct acm *acm, struct urb *urb) { + unsigned long flags; + if (!urb->actual_length) return; + spin_lock_irqsave(&acm->read_lock, flags); tty_insert_flip_string(&acm->port, urb->transfer_buffer, urb->actual_length); + spin_unlock_irqrestore(&acm->read_lock, flags); + tty_flip_buffer_push(&acm->port); }