On Fri, 22 Jan 2021 at 17:43, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
>
> Quoting Matthew Auld (2021-01-22 17:35:46)
> > Throw it into a simple helper, and throw a warning if we encounter an
> > object which has been initialised with an object size that exceeds our
> > limit of INT_MAX pages.
> >
> > Suggested-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 9 +------
> > drivers/gpu/drm/i915/gem/i915_gem_object.c | 2 ++
> > drivers/gpu/drm/i915/gem/i915_gem_object.h | 26 +++++++++++++++++++++
> > drivers/gpu/drm/i915/gem/i915_gem_region.c | 12 +---------
> > drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 16 +------------
> > 5 files changed, 31 insertions(+), 34 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> > index dc11497f830b..5cc8a0b2387f 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> > @@ -244,14 +244,7 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
> > }
> > }
> >
> > - /*
> > - * 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 (dma_buf->size >> PAGE_SHIFT > INT_MAX)
> > + if (i915_gem_object_size_2big(dma_buf->size))
> > return ERR_PTR(-E2BIG);
> >
> > /* need to attach */
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> > index 70f798405f7f..d3702ea8c6aa 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> > @@ -62,6 +62,8 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj,
> > const struct drm_i915_gem_object_ops *ops,
> > struct lock_class_key *key)
> > {
> > + GEM_CHECK_SIZE_OVERFLOW(obj->base.size);
> > +
> > __mutex_init(&obj->mm.lock, ops->name ?: "obj->mm.lock", key);
> >
> > spin_lock_init(&obj->vma.lock);
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> > index d0ae834d787a..d9cef56533ca 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> > @@ -16,6 +16,32 @@
> > #include "i915_gem_gtt.h"
> > #include "i915_vma_types.h"
> >
> > +/*
> > + * 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!
> > + *
> > + * Aside from our own locals (for which we have no excuse!):
> > + * - sg_table embeds unsigned int for num_pages
> > + * - get_user_pages*() mixed ints with longs
> > + */
> > +#define GEM_CHECK_SIZE_OVERFLOW(sz) \
> > + GEM_WARN_ON((sz) >> PAGE_SHIFT > INT_MAX)
> > +
> > +static inline bool i915_gem_object_size_2big(u64 size)
> > +{
> > + struct drm_i915_gem_object *obj;
> > +
> > + if (size >> PAGE_SHIFT > INT_MAX)
> > + return true;
>
> Macro here^
>
> Make it easy to grep, everybody gets a warning as a reminder to fix it.
> And a prize to whoever does manage to trigger the warning.
But this code is user triggable, like with igt("create-massive")? What
am I missing?
>
> > +
> > + if (overflows_type(size, obj->base.size))
> > + return true;
> > +
> > + return false;
> > +}
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