[Intel-gfx] [PATCH] drm/i915: Add checks to prevent NULL pointer dereference

[Harish Chegondi]

__sg_next() returns NULL if the input sg entry is the last entry in the
list. Check the return pointer from __sg_next() to prevent NULL pointer
dereference.

Cc: Matthew Auld <matthew.auld at intel.com>
Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Signed-off-by: Harish Chegondi <harish.chegondi at intel.com>
---
 drivers/gpu/drm/i915/i915_scatterlist.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_scatterlist.c b/drivers/gpu/drm/i915/i915_scatterlist.c
index 41f2adb6a583..da9322c5d5f7 100644
--- a/drivers/gpu/drm/i915/i915_scatterlist.c
+++ b/drivers/gpu/drm/i915/i915_scatterlist.c
@@ -112,6 +112,11 @@ struct i915_refct_sgt *i915_rsgt_from_mm_node(const struct drm_mm_node *node,
 			if (st->nents)
 				sg = __sg_next(sg);
 
+			if (!sg) {
+				sg_free_table(st);
+				i915_refct_sgt_put(rsgt);
+				return ERR_PTR(-EFAULT);
+			}
 			sg_dma_address(sg) = region_start + offset;
 			sg_dma_len(sg) = 0;
 			sg->length = 0;
@@ -191,6 +196,11 @@ struct i915_refct_sgt *i915_rsgt_from_buddy_resource(struct ttm_resource *res,
 				if (st->nents)
 					sg = __sg_next(sg);
 
+				if (!sg) {
+					sg_free_table(st);
+					i915_refct_sgt_put(rsgt);
+					return ERR_PTR(-EFAULT);
+				}
 				sg_dma_address(sg) = region_start + offset;
 				sg_dma_len(sg) = 0;
 				sg->length = 0;
-- 
2.31.1