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Date:   Fri, 27 Apr 2018 14:06:58 +0200
From:   Wolfram Sang <wsa@the-dreams.de>
To:     Alexander Popov <alex.popov@linux.com>
Cc:     Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= 
        <u.kleine-koenig@pengutronix.de>, linux-i2c@vger.kernel.org,
        linux-kernel@vger.kernel.org, sil2review@lists.osadl.org,
        Dmitry Vyukov <dvyukov@google.com>, syzkaller@googlegroups.com
Subject: Re: [v2 1/1] i2c: dev: prevent ZERO_SIZE_PTR deref in
 i2cdev_ioctl_rdwr()
Message-ID: <20180427120658.wi32f7margtfazzp@ninjato>
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On Thu, Apr 19, 2018 at 03:29:22PM +0300, Alexander Popov wrote:
> i2cdev_ioctl_rdwr() allocates i2c_msg.buf using memdup_user(), which
> returns ZERO_SIZE_PTR if i2c_msg.len is zero.
>=20
> 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.
>=20
> Let's check the len against zero before dereferencing buf pointer.
>=20
> This issue was triggered by syzkaller.
>=20
> Signed-off-by: Alexander Popov <alex.popov@linux.com>

Applied to for-current with the arithmetic expression changed to '< 1'
to keep in sync with the previous one. Will push out soon, so you can
double check if you are interested.

Thanks for the debugging, Alexander!


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