[PATCH 5.4 082/104] drm/i915/userptr: fix size calculation

[Greg Kroah-Hartman]

From: Matthew Auld <matthew.auld@xxxxxxxxx>

commit ecc4d2a52df65479de5e333a9065ed02202a400f upstream.

If we create a rather large userptr object(e.g 1ULL << 32) we might
shift past the type-width of num_pages: (int)num_pages << PAGE_SHIFT,
resulting in a totally bogus sg_table, which fortunately will eventually
manifest as:

gen8_ppgtt_insert_huge:463 GEM_BUG_ON(iter->sg->length < page_size)
kernel BUG at drivers/gpu/drm/i915/gt/gen8_ppgtt.c:463!

v2: more unsigned long
    prefer I915_GTT_PAGE_SIZE

Fixes: 5cc9ed4b9a7a ("drm/i915: Introduce mapping of user pages into video memory (userptr) ioctl")
Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20200117132413.1170563-2-matthew.auld@xxxxxxxxx
(cherry picked from commit 8e78871bc1e5efec22c950d3fd24ddb63d4ff28a)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/i915/gem/i915_gem_userptr.c |    9 +++++----
 drivers/gpu/drm/i915/i915_gem_gtt.c         |    2 ++
 2 files changed, 7 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
@@ -427,7 +427,7 @@ struct get_pages_work {
 
 static struct sg_table *
 __i915_gem_userptr_alloc_pages(struct drm_i915_gem_object *obj,
-			       struct page **pvec, int num_pages)
+			       struct page **pvec, unsigned long num_pages)
 {
 	unsigned int max_segment = i915_sg_segment_size();
 	struct sg_table *st;
@@ -473,9 +473,10 @@ __i915_gem_userptr_get_pages_worker(stru
 {
 	struct get_pages_work *work = container_of(_work, typeof(*work), work);
 	struct drm_i915_gem_object *obj = work->obj;
-	const int npages = obj->base.size >> PAGE_SHIFT;
+	const unsigned long npages = obj->base.size >> PAGE_SHIFT;
+	unsigned long pinned;
 	struct page **pvec;
-	int pinned, ret;
+	int ret;
 
 	ret = -ENOMEM;
 	pinned = 0;
@@ -578,7 +579,7 @@ __i915_gem_userptr_get_pages_schedule(st
 
 static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
 {
-	const int num_pages = obj->base.size >> PAGE_SHIFT;
+	const unsigned long num_pages = obj->base.size >> PAGE_SHIFT;
 	struct mm_struct *mm = obj->userptr.mm->mm;
 	struct page **pvec;
 	struct sg_table *pages;
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -1178,6 +1178,7 @@ gen8_ppgtt_insert_pte(struct i915_ppgtt
 	pd = i915_pd_entry(pdp, gen8_pd_index(idx, 2));
 	vaddr = kmap_atomic_px(i915_pt_entry(pd, gen8_pd_index(idx, 1)));
 	do {
+		GEM_BUG_ON(iter->sg->length < I915_GTT_PAGE_SIZE);
 		vaddr[gen8_pd_index(idx, 0)] = pte_encode | iter->dma;
 
 		iter->dma += I915_GTT_PAGE_SIZE;
@@ -1657,6 +1658,7 @@ static void gen6_ppgtt_insert_entries(st
 
 	vaddr = kmap_atomic_px(i915_pt_entry(pd, act_pt));
 	do {
+		GEM_BUG_ON(iter.sg->length < I915_GTT_PAGE_SIZE);
 		vaddr[act_pte] = pte_encode | GEN6_PTE_ADDR_ENCODE(iter.dma);
 
 		iter.dma += I915_GTT_PAGE_SIZE;