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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 289C8C4CECD for ; Fri, 20 Sep 2019 14:31:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F3E4C206C2 for ; Fri, 20 Sep 2019 14:31:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391074AbfITObS (ORCPT ); Fri, 20 Sep 2019 10:31:18 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:36908 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388396AbfITOZQ (ORCPT ); Fri, 20 Sep 2019 10:25:16 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1iBJqT-000512-DD; Fri, 20 Sep 2019 15:25:13 +0100 Received: from ben by deadeye with local (Exim 4.92.1) (envelope-from ) id 1iBJqE-0007ts-RA; Fri, 20 Sep 2019 15:24:58 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Greg Kroah-Hartman" , "Oliver Neukum" Date: Fri, 20 Sep 2019 15:23:35 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 066/132] cdc-acm: fix race between callback and unthrottle In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.74-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Oliver Neukum commit 36e59e0d70d6150e7a2155c54612ea875e88ce8d upstream. Abn URB may be may marked free only after the buffer has been processed or there is a small window during which it could be submitted on another CPU and overwrite an unprocessed buffer Signed-off-by: Oliver Neukum Signed-off-by: Greg Kroah-Hartman [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- drivers/usb/class/cdc-acm.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -419,19 +419,21 @@ static void acm_read_bulk_callback(struc struct acm_rb *rb = urb->context; struct acm *acm = rb->instance; unsigned long flags; + int status = urb->status; dev_vdbg(&acm->data->dev, "%s - urb %d, len %d\n", __func__, rb->index, urb->actual_length); - set_bit(rb->index, &acm->read_urbs_free); if (!acm->dev) { + set_bit(rb->index, &acm->read_urbs_free); dev_dbg(&acm->data->dev, "%s - disconnected\n", __func__); return; } if (urb->status) { + set_bit(rb->index, &acm->read_urbs_free); dev_dbg(&acm->data->dev, "%s - non-zero urb status: %d\n", - __func__, urb->status); + __func__, status); if ((urb->status != -ENOENT) || (urb->actual_length == 0)) return; } @@ -439,6 +441,12 @@ static void acm_read_bulk_callback(struc usb_mark_last_busy(acm->dev); acm_process_read_urb(acm, urb); + /* + * Unthrottle may run on another CPU which needs to see events + * in the same order. Submission has an implict barrier + */ + smp_mb__before_atomic(); + set_bit(rb->index, &acm->read_urbs_free); /* throttle device if requested by tty */ spin_lock_irqsave(&acm->read_lock, flags);