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 E7E02CA9EC9 for ; Mon, 4 Nov 2019 21:49:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B2E4D217F4 for ; Mon, 4 Nov 2019 21:49:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572904183; bh=/Ys8JP9U4GHYI+d6hD1pxpt4rHg0+OqteyS7APFzBx8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=JHQkYTtKeG/qXEufNpzuwR1I1RnSDoZIZ3ARgxr4Wo9mmeBbbnsp9jB9Wf9oKitmL P9b6q81BSQmyv2q3S19KG7SLC54NV12qWDxo6U4aaYBx6lSuKupz7qhMRtvtFdwKwc Mu+xl6bX8fg8dlVAxcM9PsVee83uM1eJfkrirIdQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387485AbfKDVtm (ORCPT ); Mon, 4 Nov 2019 16:49:42 -0500 Received: from mail.kernel.org ([198.145.29.99]:41094 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387466AbfKDVtj (ORCPT ); Mon, 4 Nov 2019 16:49:39 -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 BC65C20B7C; Mon, 4 Nov 2019 21:49:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572904178; bh=/Ys8JP9U4GHYI+d6hD1pxpt4rHg0+OqteyS7APFzBx8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2PZ1Ea33lQv/c+XZw654KIwdTMKeHaQiodguyN+y29zTdUcuFvOltC2MTuWwxw9Be 4Ig9b34FvAEAd0MLCIrIOy0Fl8CuajQOLyasI1DaF/xBYDnN3n4sRthk6ORdY4Wwb7 V7KrJ4x7mNmaDozsJXnKl7d08aWTYhv8BfTpsb2I= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Johan Hovold Subject: [PATCH 4.4 30/46] USB: ldusb: fix ring-buffer locking Date: Mon, 4 Nov 2019 22:45:01 +0100 Message-Id: <20191104211902.812567843@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191104211830.912265604@linuxfoundation.org> References: <20191104211830.912265604@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 @@ -499,11 +499,11 @@ 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);