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

From: Sven Joachim <svenjoac@gmx.de>
To: Zhaowei Yuan <zhaowei.yuan@samsung.com>
Cc: dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm: fix NULL pointer access by wrong ioctl
Date: Mon, 30 Jun 2014 18:04:43 +0200	[thread overview]
Message-ID: <87y4wez8mc.fsf@turtle.gmx.de> (raw)
In-Reply-To: <1403073239-6493-1-git-send-email-zhaowei.yuan@samsung.com> (Zhaowei Yuan's message of "Wed, 18 Jun 2014 14:33:59 +0800")

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@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
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