Re: [v2 1/1] i2c: dev: prevent ZERO_SIZE_PTR deref in i2cdev_ioctl_rdwr()

From: Wolfram Sang
Date: Fri Apr 27 2018 - 08:07:07 EST

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.
> 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 <alex.popov@xxxxxxxxx>

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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