From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Popov Subject: [PATCH 1/1] i2c: dev: check i2c_msg len before memdup_user() to prevent ZERO_SIZE_PTR deref Date: Wed, 18 Apr 2018 03:16:45 +0300 Message-ID: <1524010605-21552-1-git-send-email-alex.popov@linux.com> Return-path: Sender: linux-kernel-owner@vger.kernel.org To: Wolfram Sang , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, sil2review@lists.osadl.org, Dmitry Vyukov , Alexander Popov List-Id: linux-i2c@vger.kernel.org Currently i2cdev_ioctl_rdwr() doesn't check i2c_msg len against zero before calling memdup_user(). If this len is zero memdup_user() returns ZERO_SIZE_PTR, which is later considered as valid since IS_ERR(ZERO_SIZE_PTR) is false. That causes ZERO_SIZE_PTR deref oops. Let's check i2c_msg len against zero before calling memdup_user(). This issue was triggered by syzkaller. Signed-off-by: Alexander Popov --- drivers/i2c/i2c-dev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c index 036a03f..b9b6715 100644 --- a/drivers/i2c/i2c-dev.c +++ b/drivers/i2c/i2c-dev.c @@ -252,8 +252,8 @@ static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client, res = 0; for (i = 0; i < nmsgs; i++) { - /* Limit the size of the message to a sane amount */ - if (msgs[i].len > 8192) { + /* Check that the size is sane */ + if (!msgs[i].len || msgs[i].len > 8192) { res = -EINVAL; break; } -- 2.7.4