On Mon, 25 Jul 2022, Gwan-gyeong Mun <gwan-gyeong.mun@xxxxxxxxx> wrote:
> There is an impedance mismatch between the first/last valid page
> frame number of ttm place in unsigned and our memory/page accounting in
> unsigned long.
> As the object size is under the control of userspace, we have to be prudent
> and catch the conversion errors.
> To catch the implicit truncation as we switch from unsigned long to
> unsigned, we use overflows_type check and report E2BIG or overflow_type
> prior to the operation.
>
> v3: Not to change execution inside a macro. (Mauro)
> Add safe_conversion_gem_bug_on() macro and remove temporal
> SAFE_CONVERSION() macro.
>
> v4: Fix unhandled GEM_BUG_ON() macro call from safe_conversion_gem_bug_on()
>
> Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@xxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
> Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> Reviewed-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
> Reviewed-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 6 +++---
> drivers/gpu/drm/i915/i915_gem.h | 4 ++++
> drivers/gpu/drm/i915/intel_region_ttm.c | 20 +++++++++++++++++---
> 3 files changed, 24 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> index 9f2be1892b6c..88f2887627dc 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> @@ -140,14 +140,14 @@ i915_ttm_place_from_region(const struct intel_memory_region *mr,
> if (flags & I915_BO_ALLOC_CONTIGUOUS)
> place->flags |= TTM_PL_FLAG_CONTIGUOUS;
> if (offset != I915_BO_INVALID_OFFSET) {
> - place->fpfn = offset >> PAGE_SHIFT;
> - place->lpfn = place->fpfn + (size >> PAGE_SHIFT);
> + safe_conversion_gem_bug_on(&place->fpfn, offset >> PAGE_SHIFT);
> + safe_conversion_gem_bug_on(&place->lpfn, place->fpfn + (size >> PAGE_SHIFT));
So the natural thing would be to have and use two orthogonal helpers, a
safe_conversion predicate and a warn:
GEM_BUG_ON(!safe_conversion(...));
or even:
if (GEM_BUG_ON(!safe_conversion(...)))
/* ... */
But GEM_BUG_ON() is surprising and does not follow the same pattern as
WARN_ON/BUG_ON. *sigh*
BR,
Jani.
> } else if (mr->io_size && mr->io_size < mr->total) {
> if (flags & I915_BO_ALLOC_GPU_ONLY) {
> place->flags |= TTM_PL_FLAG_TOPDOWN;
> } else {
> place->fpfn = 0;
> - place->lpfn = mr->io_size >> PAGE_SHIFT;
> + safe_conversion_gem_bug_on(&place->lpfn, mr->io_size >> PAGE_SHIFT);
> }
> }
> }
> diff --git a/drivers/gpu/drm/i915/i915_gem.h b/drivers/gpu/drm/i915/i915_gem.h
> index 68d8d52bd541..327dacedd5d1 100644
> --- a/drivers/gpu/drm/i915/i915_gem.h
> +++ b/drivers/gpu/drm/i915/i915_gem.h
> @@ -83,5 +83,9 @@ struct drm_i915_private;
> #endif
>
> #define I915_GEM_IDLE_TIMEOUT (HZ / 5)
> +#define safe_conversion_gem_bug_on(ptr, value) !({ \
> + safe_conversion(ptr, value) ? 0 \
> + : (({ GEM_BUG_ON(overflows_type(value, *ptr)); }), 1); \
> +})
>
> #endif /* __I915_GEM_H__ */
> diff --git a/drivers/gpu/drm/i915/intel_region_ttm.c b/drivers/gpu/drm/i915/intel_region_ttm.c
> index 575d67bc6ffe..f0d143948725 100644
> --- a/drivers/gpu/drm/i915/intel_region_ttm.c
> +++ b/drivers/gpu/drm/i915/intel_region_ttm.c
> @@ -209,14 +209,26 @@ intel_region_ttm_resource_alloc(struct intel_memory_region *mem,
> if (flags & I915_BO_ALLOC_CONTIGUOUS)
> place.flags |= TTM_PL_FLAG_CONTIGUOUS;
> if (offset != I915_BO_INVALID_OFFSET) {
> - place.fpfn = offset >> PAGE_SHIFT;
> - place.lpfn = place.fpfn + (size >> PAGE_SHIFT);
> + if (!safe_conversion_gem_bug_on(&place.fpfn,
> + offset >> PAGE_SHIFT)) {
> + ret = -E2BIG;
> + goto out;
> + }
> + if (!safe_conversion_gem_bug_on(&place.lpfn,
> + place.fpfn + (size >> PAGE_SHIFT))) {
> + ret = -E2BIG;
> + goto out;
> + }
> } else if (mem->io_size && mem->io_size < mem->total) {
> if (flags & I915_BO_ALLOC_GPU_ONLY) {
> place.flags |= TTM_PL_FLAG_TOPDOWN;
> } else {
> place.fpfn = 0;
> - place.lpfn = mem->io_size >> PAGE_SHIFT;
> + if (!safe_conversion_gem_bug_on(&place.lpfn,
> + mem->io_size >> PAGE_SHIFT)) {
> + ret = -E2BIG;
> + goto out;
> + }
> }
> }
>
> @@ -224,6 +236,8 @@ intel_region_ttm_resource_alloc(struct intel_memory_region *mem,
> mock_bo.bdev = &mem->i915->bdev;
>
> ret = man->func->alloc(man, &mock_bo, &place, &res);
> +
> +out:
> if (ret == -ENOSPC)
> ret = -ENXIO;
> if (!ret)
--
Jani Nikula, Intel Open Source Graphics Center
