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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 7BE95C67790 for ; Fri, 27 Jul 2018 10:03:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 21D6020894 for ; Fri, 27 Jul 2018 10:03:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 21D6020894 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389314AbeG0LYM (ORCPT ); Fri, 27 Jul 2018 07:24:12 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:34470 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730568AbeG0LYL (ORCPT ); Fri, 27 Jul 2018 07:24:11 -0400 Received: from localhost (unknown [89.188.5.116]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 304FDBB6; Fri, 27 Jul 2018 10:03:01 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Samuel Thibault , Jann Horn Subject: [PATCH 4.14 33/48] staging: speakup: fix wraparound in uaccess length check Date: Fri, 27 Jul 2018 12:00:18 +0200 Message-Id: <20180727095921.983735959@linuxfoundation.org> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180727095918.503549522@linuxfoundation.org> References: <20180727095918.503549522@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Samuel Thibault commit b96fba8d5855c3617adbfb43ca4723a808cac954 upstream. If softsynthx_read() is called with `count < 3`, `count - 3` wraps, causing the loop to copy as much data as available to the provided buffer. If softsynthx_read() is invoked through sys_splice(), this causes an unbounded kernel write; but even when userspace just reads from it normally, a small size could cause userspace crashes. Fixes: 425e586cf95b ("speakup: add unicode variant of /dev/softsynth") Cc: stable@vger.kernel.org Signed-off-by: Samuel Thibault Signed-off-by: Jann Horn Signed-off-by: Greg Kroah-Hartman --- drivers/staging/speakup/speakup_soft.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/drivers/staging/speakup/speakup_soft.c +++ b/drivers/staging/speakup/speakup_soft.c @@ -207,11 +207,15 @@ static ssize_t softsynthx_read(struct fi int chars_sent = 0; char __user *cp; char *init; + size_t bytes_per_ch = unicode ? 3 : 1; u16 ch; int empty; unsigned long flags; DEFINE_WAIT(wait); + if (count < bytes_per_ch) + return -EINVAL; + spin_lock_irqsave(&speakup_info.spinlock, flags); while (1) { prepare_to_wait(&speakup_event, &wait, TASK_INTERRUPTIBLE); @@ -237,7 +241,7 @@ static ssize_t softsynthx_read(struct fi init = get_initstring(); /* Keep 3 bytes available for a 16bit UTF-8-encoded character */ - while (chars_sent <= count - 3) { + while (chars_sent <= count - bytes_per_ch) { if (speakup_info.flushing) { speakup_info.flushing = 0; ch = '\x18';