[PATCH] drm: fix NULL pointer access by wrong ioctl

[Sven Joachim]

On 2014-06-18 08:33 +0200, Zhaowei Yuan wrote:

> If user uses wrong ioctl command with _IOC_NONE and argument size
> greater than 0, it can cause NULL pointer access from memset of line
> 463. If _IOC_NONE, don't memset to 0 for kdata.
>
> Signed-off-by: Zhaowei Yuan <zhaowei.yuan at samsung.com>
> ---
>  drivers/gpu/drm/drm_drv.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>  mode change 100644 => 100755 drivers/gpu/drm/drm_drv.c

The mode change certainly was not intentional, was it?  Just noticed it
when I pulled 3.16-rc3 from Linus…

> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> old mode 100644
> new mode 100755
> index 2ab782c..1a92bcb
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -459,8 +459,9 @@ long drm_ioctl(struct file *filp,
>  				retcode = -EFAULT;
>  				goto err_i1;
>  			}
> -		} else
> +		} else if (cmd & IOC_OUT) {
>  			memset(kdata, 0, usize);
> +		}
>
>  		if (ioctl->flags & DRM_UNLOCKED)
>  			retcode = func(dev, kdata, file_priv);


Cheers,
       Sven