Re: [PATCH] drm/i915/ppgtt: Prevent NULL deref in reset ioctl

Ben Widawsky
2013-12-20T06:56:00Z

On Fri, Dec 20, 2013 at 07:05:10AM +0100, Daniel Vetter wrote:
> On Fri, Dec 20, 2013 at 12:22 AM, Ben Widawsky
> <benjamin.widawsky@intel.com> wrote:
> > ctx = i915_gem_context_get(file->driver_priv, args->ctx_id);
> > - if (IS_ERR(ctx)) {
> > + if (IS_ERR_OR_NULL(ctx)) {
>
> We now have half the callers check for IS_ERR and the others not.
> Afaics i915_gem_context_get can only return NULL or a real context
> though. Also from a quite read the expected error for a lookup failure
> is ENOENT (and there seems to be a testcase for this).
> -Daniel

To your first point:
I think checking null is always the right thing currently, but for
future proofing, IS_ERR_OR_NULL is really the right thing. After his
patch, I believe only i915_gem_context_destroy_ioctl is still incorrect.

To the second:
This is only based on my memory, so feel free to change whatever you
need. When I retuned -ENXIO, the test failed.

It should be:
return ctx ? PTR_ERR(ctx) : -ENOENT;

I had
return ctx ? PTR_ERR(ctx) : -ENXIO;
which made the subtest fail. However, as we've noted, this itself was
not correct. Try the return above.

--
Ben Widawsky, Intel Open Source Technology Center