linux-kernel - Re: [PATCH] drm/i915: Sanity check incoming ioctl data for a NULL pointer

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Date:	Thu, 14 Mar 2013 15:39:28 +0200
From:	Tommi Rantala <tt.rantala@...il.com>
To:	Chris Wilson <chris@...is-wilson.co.uk>
Cc:	Daniel Vetter <daniel.vetter@...ll.ch>,
	David Airlie <airlied@...ux.ie>,
	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: [PATCH] drm/i915: Sanity check incoming ioctl data for a NULL pointer

2013/3/14 Chris Wilson <chris@...is-wilson.co.uk>:
> In order to prevent a potential NULL deference with hostile userspace,
> we need to check whether the ioctl was passed an invalid args pointer.
>
> Reported-by: Tommi Rantala <tt.rantala@...il.com>
> Link: http://lkml.kernel.org/r/CA+ydwtpuBvbwxbt-tdgPUvj1EU7itmCHo_2B3w13HkD5+jWKow@mail.gmail.com
> Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>

Thanks, looks good. I still see a flood of oopses from the other
ioctls, so it's a bit difficult to test this patch properly.

> ---
>  drivers/gpu/drm/i915/i915_gem_execbuffer.c |   11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index 365e41a..9f5602e 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -1103,7 +1103,11 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
>         struct drm_i915_gem_exec_object2 *exec2_list = NULL;
>         int ret, i;
>
> -       if (args->buffer_count < 1) {
> +       if (args == NULL)
> +               return -EINVAL;
> +
> +       if (args->buffer_count < 1 ||
> +           args->buffer_count > INT_MAX / sizeof(*exec2_list)) {
>                 DRM_DEBUG("execbuf with %d buffers\n", args->buffer_count);
>                 return -EINVAL;
>         }
> @@ -1182,8 +1186,11 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data,
>         struct drm_i915_gem_exec_object2 *exec2_list = NULL;
>         int ret;
>
> +       if (args == NULL)
> +               return -EINVAL;
> +
>         if (args->buffer_count < 1 ||
> -           args->buffer_count > UINT_MAX / sizeof(*exec2_list)) {
> +           args->buffer_count > INT_MAX / sizeof(*exec2_list)) {
>                 DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
>                 return -EINVAL;
>         }
> --
> 1.7.10.4
>
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