On Thu, Mar 14, 2013 at 12:59:57PM +0000, Chris Wilson wrote:
> 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.rant...@gmail.com>
> Link:
> http://lkml.kernel.org/r/ca+ydwtpubvbwxbt-tdgpuvj1eu7itmcho_2b3w13hkd5+jw...@mail.gmail.com
> Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
> ---
> 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;
> }
Why did you change UINT_MAX to INT_MAX? TBH, I'm confused what we're
trying to achieve, and why we need anything other than:
if (!args->buffer_count)
I'm also not seeing how the NULL checks are needed since at least it
seems to be for execbuffer (IOW) we could never have NULL args.
if (cmd & (IOC_IN | IOC_OUT)) {
if (asize <= sizeof(stack_kdata)) {
kdata = stack_kdata;
} else {
kdata = kmalloc(asize, GFP_KERNEL);
if (!kdata) {
retcode = -ENOMEM;
goto err_i1;
}
}
if (asize > usize)
memset(kdata + usize, 0, asize - usize);
}
Sorry if these are stupid questions.
--
Ben Widawsky, Intel Open Source Technology Center
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