From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751463AbcCCF7S (ORCPT ); Thu, 3 Mar 2016 00:59:18 -0500 Received: from mail-pf0-f173.google.com ([209.85.192.173]:36005 "EHLO mail-pf0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751002AbcCCF7R (ORCPT ); Thu, 3 Mar 2016 00:59:17 -0500 From: Gwendal Grignou To: olofj@chromium.org, alan@lxorguk.ukuu.org.uk, javier.martinez@collabora.co.uk Cc: linux-kernel@vger.kernel.org Subject: [PATCH] platform/chrome: cros_ec_dev - Fix security issue Date: Wed, 2 Mar 2016 21:58:56 -0800 Message-Id: <1456984736-19811-1-git-send-email-gwendal@chromium.org> X-Mailer: git-send-email 2.7.0.rc3.207.g0ac5344 In-Reply-To: <20160301203338.360a3487@www.etchedpixels.co.uk> References: <20160301203338.360a3487@www.etchedpixels.co.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add a check to prevent memory scribbe when sending an ioctl with .insize set so large that memory allocation argument overflows. Signed-off-by: Gwendal Grignou --- drivers/platform/chrome/cros_ec_dev.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c index d45cd25..86d6373 100644 --- a/drivers/platform/chrome/cros_ec_dev.c +++ b/drivers/platform/chrome/cros_ec_dev.c @@ -131,13 +131,23 @@ static ssize_t ec_device_read(struct file *filp, char __user *buffer, static long ec_device_ioctl_xcmd(struct cros_ec_dev *ec, void __user *arg) { long ret; + size_t data_size; struct cros_ec_command u_cmd; struct cros_ec_command *s_cmd; if (copy_from_user(&u_cmd, arg, sizeof(u_cmd))) return -EFAULT; - s_cmd = kmalloc(sizeof(*s_cmd) + max(u_cmd.outsize, u_cmd.insize), + /* + * Prevent mallicious attack where .inside is so big that amount + * kmalloc'ed rollover, allowing memcpy to write beyond the allocated + * space. + */ + data_size = max(u_cmd.outsize, u_cmd.insize); + if (data_size + sizeof(*s_cmd) < data_size) + return -EINVAL; + + s_cmd = kmalloc(sizeof(*s_cmd) + data_size, GFP_KERNEL); if (!s_cmd) return -ENOMEM; -- 2.7.0.rc3.207.g0ac5344