[Intel-gfx] [PATCH v2 1/2] drm/i915/userptr: add user_size limit check

[Matthew Auld]

On Thu, 16 Jan 2020 at 21:19, Chris Wilson <chris at chris-wilson.co.uk> wrote:
>
> Quoting Matthew Auld (2020-01-16 20:31:49)
> > Don't allow a mismatch between obj->base.size/vma->size and the actual
> > number of pages for the backing store, which is limited to INT_MAX
> > pages.
> >
> > Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> > index e5558af111e2..fef96a303d9d 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> > @@ -768,6 +768,18 @@ i915_gem_userptr_ioctl(struct drm_device *dev,
> >         if (args->flags & ~(I915_USERPTR_READ_ONLY |
> >                             I915_USERPTR_UNSYNCHRONIZED))
> >                 return -EINVAL;
> > +       /*
> > +        * XXX: There is a prevalence of the assumption that we fit the
> > +        * object's page count inside a 32bit _signed_ variable. Let's document
> > +        * this and catch if we ever need to fix it. In the meantime, if you do
> > +        * spot such a local variable, please consider fixing!
> > +        */
> > +
> > +       if (args->user_size >> PAGE_SHIFT > INT_MAX)
> > +               return -E2BIG;
>
> I'm convinced that the following patch is the last bug (excusing
> i915_gem_internal.c), and think we should commit to removing this limit.

You mean on our side? There is still all the sg_table stuff,
__get_user_pages_fast etc.

> -Chris
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