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

[Kleber Souza]

On 11/07/18 16:18, Colin King wrote:
> From: Colin Ian King <colin.king at canonical.com>
>
> BugLink: https://bugs.launchpad.net/bugs/1797546
>
> 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>
> Reviewed-by: David Herrmann <dh.herrmann at gmail.com>
> Cc: <stable at vger.kernel.org>
> Signed-off-by: Dave Airlie <airlied at redhat.com>
> (backported from commit 1539fb9bd405ee32282ea0a38404f9e008ac5b7a)
> Signed-off-by: Colin Ian King <colin.king at canonical.com>

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>

> ---
>  drivers/gpu/drm/drm_drv.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index d9137e4..ef65779 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -383,8 +383,9 @@ 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);