From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752511AbeDSM3m (ORCPT ); Thu, 19 Apr 2018 08:29:42 -0400 Received: from mail-wr0-f194.google.com ([209.85.128.194]:45418 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751953AbeDSM3l (ORCPT ); Thu, 19 Apr 2018 08:29:41 -0400 X-Google-Smtp-Source: AIpwx4/Zx9WqJcwTTjihtA7RHVzilc6tuTO930yqtYR9aWxM6MwWV24j3/1rL0BNOiTCAejJ+Hr9ZA== From: Alexander Popov To: Wolfram Sang , =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, sil2review@lists.osadl.org, Dmitry Vyukov , syzkaller@googlegroups.com, Alexander Popov Subject: [v2 1/1] i2c: dev: prevent ZERO_SIZE_PTR deref in i2cdev_ioctl_rdwr() Date: Thu, 19 Apr 2018 15:29:22 +0300 Message-Id: <1524140962-25639-1-git-send-email-alex.popov@linux.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org i2cdev_ioctl_rdwr() allocates i2c_msg.buf using memdup_user(), which returns ZERO_SIZE_PTR if i2c_msg.len is zero. Currently i2cdev_ioctl_rdwr() always dereferences the buf pointer in case of I2C_M_RD | I2C_M_RECV_LEN transfer. That causes a kernel oops in case of zero len. Let's check the len against zero before dereferencing buf pointer. This issue was triggered by syzkaller. Signed-off-by: Alexander Popov --- drivers/i2c/i2c-dev.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c index 036a03f..5790bc8 100644 --- a/drivers/i2c/i2c-dev.c +++ b/drivers/i2c/i2c-dev.c @@ -280,6 +280,7 @@ static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client, */ if (msgs[i].flags & I2C_M_RECV_LEN) { if (!(msgs[i].flags & I2C_M_RD) || + !msgs[i].len || msgs[i].buf[0] < 1 || msgs[i].len < msgs[i].buf[0] + I2C_SMBUS_BLOCK_MAX) { -- 2.7.4