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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 A1A8BCA9EC9 for ; Mon, 4 Nov 2019 22:18:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 77237204EC for ; Mon, 4 Nov 2019 22:18:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572905897; bh=DCUP1rMU0M3Y1yX9lQVOzFNO32AQS16GN6flBTYc580=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=wDnmkP8BvFS8btkDrhQMCtv0Hpt4Gu/G9PpjG7uvsS3dFMQ8XU4n5Cz/Fzg/G1Pea FhjW7kzRsxUOdHgE2kfYjBTde6NvqhBL3yXm1xHGI4ySQKVgqBoVbJtFWJEPUGTChj /7EHMXwub/Kq4o5NxaDZiyinQyjOd5HbmXUwU6QU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389772AbfKDWSN (ORCPT ); Mon, 4 Nov 2019 17:18:13 -0500 Received: from mail.kernel.org ([198.145.29.99]:60366 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389197AbfKDWCE (ORCPT ); Mon, 4 Nov 2019 17:02:04 -0500 Received: from localhost (6.204-14-84.ripe.coltfrance.com [84.14.204.6]) (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 68A1E20659; Mon, 4 Nov 2019 22:02:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572904923; bh=DCUP1rMU0M3Y1yX9lQVOzFNO32AQS16GN6flBTYc580=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jze5VVGXcmhEvW2vXZX6nTZ5beiw+UzRyMhIHmNE3TS0fO51TM3nx4w0gj5Txq6ab 26eq35/ey/IROJMC3gW4Zkf+cV2SbH/IBOetuAeo0SSYZrrGTeKio9Oh3Ng6kFfplU BWBpV4QNxt5OL1I4auXKe/SlWjY+1+puSnUeobjA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Johan Hovold Subject: [PATCH 4.19 117/149] USB: ldusb: fix ring-buffer locking Date: Mon, 4 Nov 2019 22:45:10 +0100 Message-Id: <20191104212144.528426176@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191104212126.090054740@linuxfoundation.org> References: <20191104212126.090054740@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Johan Hovold commit d98ee2a19c3334e9343df3ce254b496f1fc428eb upstream. The custom ring-buffer implementation was merged without any locking or explicit memory barriers, but a spinlock was later added by commit 9d33efd9a791 ("USB: ldusb bugfix"). The lock did not cover the update of the tail index once the entry had been processed, something which could lead to memory corruption on weakly ordered architectures or due to compiler optimisations. Specifically, a completion handler running on another CPU might observe the incremented tail index and update the entry before ld_usb_read() is done with it. Fixes: 2824bd250f0b ("[PATCH] USB: add ldusb driver") Fixes: 9d33efd9a791 ("USB: ldusb bugfix") Cc: stable # 2.6.13 Signed-off-by: Johan Hovold Link: https://lore.kernel.org/r/20191022143203.5260-2-johan@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/usb/misc/ldusb.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/usb/misc/ldusb.c +++ b/drivers/usb/misc/ldusb.c @@ -495,11 +495,11 @@ static ssize_t ld_usb_read(struct file * retval = -EFAULT; goto unlock_exit; } - dev->ring_tail = (dev->ring_tail+1) % ring_buffer_size; - retval = bytes_to_read; spin_lock_irq(&dev->rbsl); + dev->ring_tail = (dev->ring_tail + 1) % ring_buffer_size; + if (dev->buffer_overflow) { dev->buffer_overflow = 0; spin_unlock_irq(&dev->rbsl);