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=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 2CFABCA9EC9 for ; Mon, 4 Nov 2019 22:08:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E940A214D8 for ; Mon, 4 Nov 2019 22:08:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572905326; bh=DCUP1rMU0M3Y1yX9lQVOzFNO32AQS16GN6flBTYc580=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=sAr4nP6a4XSuYoFpKX+HzYOyVOPl3WIRJ6ntGR883GiBKWxmLTfvSqE2wIi6aYlSn fygWT2vFBOMpdQv9bX/DQl7CzHDx9UdKhuzg1idMVFhD6JY7v1Ccc7QfPuf55VrtUU sUtAQh+86WTrK6iYliZj/NgozDrXTLKcQHLGY6KI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390285AbfKDWIo (ORCPT ); Mon, 4 Nov 2019 17:08:44 -0500 Received: from mail.kernel.org ([198.145.29.99]:41612 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390274AbfKDWIm (ORCPT ); Mon, 4 Nov 2019 17:08:42 -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 64C61214E0; Mon, 4 Nov 2019 22:08:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572905321; bh=DCUP1rMU0M3Y1yX9lQVOzFNO32AQS16GN6flBTYc580=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IT2Gi7E//NLMX1k+fPubGeIS6AATMf0U3cYBl4e048M7ktvEmhu2BzWbUqGq3bfqi vkuo2r5wwLhyZU8T8aifI3SqnM5PuvRvyhEH5etLoimBXq+SzQRfue7ET8QJ7FJE3S Qs000fwjrw8AGHlnyon+jP6oVD1xocseAyaQFrAo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Johan Hovold Subject: [PATCH 5.3 106/163] USB: ldusb: fix ring-buffer locking Date: Mon, 4 Nov 2019 22:44:56 +0100 Message-Id: <20191104212147.776449557@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191104212140.046021995@linuxfoundation.org> References: <20191104212140.046021995@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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);