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.
> +
> + if (overflows_type(size, obj->base.size))
> + return true;
> +
> + return false;
> +}
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